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BDS 2 > BDS5001: ICP > Flashcards

BDS5001: ICP Flashcards

1
Q

What are the 3 responses by dentine to injury?

A
  1. Tubular sclerosis
  2. Reactionary dentine
  3. Pulpitis
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2
Q

Explain tubular sclerosis

A

Odontoblasts retract from acid stimuli, inc. formation peritubular dentine
Occlusion of dentine tubules, walling of pulp-dentine complex from injury
Tracts D to the occlusion forming dead tracts
Appears translucent in GS due to inc. mineralisation

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3
Q

Explain reactionary dentine

A

2ndary dentine formed at pulp dentine interface, inc. distance between pulp and noxious stimuli
Low grade: deposited slowly, tubules regular
High grade: inc. rate, tubules irregular

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4
Q

What happens if odontoblasts die?

A

Eburnoid: atubular calcification formed by pulpal cells

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5
Q

Explain pulpitis

A

Very painful
Inc. blood flow, vascular dilation
Oedema
Migration of; neutrophils and macrophages (acute), plasma cells and lymphocytes (chronic)

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6
Q

Explain the pulp dentine complex response to caries when enamel is intact

A

Lesion cone shaped; lat. spread @ EDJ due to higher organic content + low F- at this region of enamel
Fissure caries dentine SAs > than smooth surface caries

Odontoblasts: TS, reactionary dentine
Lesion sterile: enamel intact, no microorganisms
Radiographically: red. pulpal vol. due to reactionary dentine; enamel demineralisation

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7
Q

Explain early cavitation dentine caries

A

After extensive subsurface demineralisation of enamel, surface # and microorganisms penetrate

Acidogenic bacteria: penetrate dentine tubules; acid diffuses ahead causing demineralisation
Proteolytic bacteria: destroy organic matrix forming liquefaction foci; multiplying bacteria lie para. to tubules

Liquefactive foci coalesce forming transfer clefts @ 90 to tubules

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8
Q

Describe advanced carious destruction

A

Destruction greater, tubular sclerosis destroyed
Bacteria penetrate almost to pulp in advance zone of sterile demineralisation
Odontoblasts may degenerate, marked pulpitis

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9
Q

For an x-ray to be justified what criteria must be met?

A
  1. Benefit to pt from diagnostic info. must outweigh detriment of exposure
  2. Expected to provide new info. to aid pt’s management or prognosis
  3. Availability and findings of previous radiographs
  4. Efficacy, benefits and risks of alternative techniques w/ same objective
  5. Benefit is directly related to diagnostic info. provided by radiograph
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10
Q

What 4 things is the diagnostic info provided by X-rays dependent on?

A
  1. Pt preparation
  2. Positioning
  3. Exposure
  4. Processing
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11
Q

Describe the ideal set up for an X-ray

A

Tooth and sensor as close as possible; further away = magnified, blurry
Parallel to each other
X-ray beam meets tooth and sensor at right angle
Position is reproducible; exactly same projection and exposure

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12
Q

What problems are faced that prevent the ideal X-ray image?

A

Tooth within bone; can’t tell direction of roots
Anatomical structures (palate, floor); can’t get direct contact w/o bending sensor
Multi-rooted teeth

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13
Q

What is a beam aiming device?

A

Piece of equipment that allows X-ray beam and film to be aligned as accurately as possible to produce reproducible images
Holds film IO and EO has ring to align collimator

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14
Q

What colour of BADs are used for each IO X-ray?

A

Blue: ant.
Red: BW
Yellow: post.

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15
Q

What are the 3 main types of IO X-ray?

A
  1. BW; caries in no. teeth and bone level
  2. PA; whole tooth; crown -> apices and bone
  3. O; occlusal table
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16
Q

Describe the paralleling technique for taking radiographs

A

Sensor placed in BAD
Positioned in mouth so parallel to long axis of tooth
X-ray tube aligned so perp to sensor

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17
Q

Compare advantages of paralleling technique and bisecting angle technique

A

Paralleling; more reproducible, easier

Bisecting; pts w/ gag reflex, can’t get holder in

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18
Q

Describe the bisecting angle technique for taking radiographs

A

Sensor placed as close to tooth as possible w/o bending
Angle b/w long axis tooth and sensor estimated and mentally bisected
X-ray tube positioned at right angle to bisecting line; central beam aimed at apex

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19
Q

What are the 2 main types of O radiographs?

A
  1. Max.; standard (60-75), oblique

2. Mand.; 90 (true), oblique, 45

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20
Q

When are max. O X-rays used?

A 
PA assessment of teeth can't tolerate IOPA
Detecting presence pathology; #, cyst
Parallax for un-erupted teeth
#s of teeth/alveolar bone
Assess antrum/roots displaced
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21
Q

When are mand. O radiographs used?

A

Presence of radiopaque calculi in submandibular ducts
Buccolingual position of teeth/pathology
Expansion caused by tumours/cysts
Assess mand. width prior to implant

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22
Q

When are pan radiographs used?

A

Assess 8s before XLA
Multiple XLAs
Ortho
Mandibular #s
TMJ problems; changes in occlusion/trauma/change in motion
Bony lesions/un-erupted tooth can’t be visualised on IO images

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23
Q

What is the focal trough/plane of a pan?

A

Area of image which is in focus, anything outside will be blurred

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24
Q

What are the 4 main disadvantages of pans?

A
  1. Image quality
  2. Operator dependent
  3. Ghost images and superimposed
  4. Inc. dose
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25
Q

What is a cephalometric radiograph?

A

Standardised reproducible radiograph that assesses relation of teeth to jaw and jaw to facial skeleton
Taken using a cephalostat

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26
Q

What are the uses of cephalometric radiographs?

A 
Ortho/orthognathic surgery;
Skeletal/soft tissue abnormalities 
Treatment planning
Monitoring progress
Assess treatment results
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27
Q

What are the 2 types of radiographs?

A
  1. Digital: in/direct

2. Conventional: manual, automatic

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28
Q

Describe solid state radiograph sensors

A

Direct digital; directly connected to computer wire/less; input info from each pixel directly to computer via analogue to digital converter
Grayscale value proportional to amount energy absorbed in scintillation layer (active layer; reacts to photons); high (black) -> low (white)

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29
Q

Describe advantages and disadvantages of SSS X-rays

A

Advantage: instant
Disadvantage: cost, bulky, difficult to position

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30
Q

Describe how phosphor plate sensors are processed

A

Phosphor layer absorbs and stores energy
Plate processed in reader; laser scans sensor, stored energy released as light
Light detected by photomultiplier tubes, converts into electrical signal
To computer via analogue to digital converter

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31
Q

What factors are important when viewing radiographs?

A 
Display; LCD, CRT
Resolution
Contrast ratio
Luminance 
DICOM; digital imaging and communication in medicine - standard, more info than jpeg
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32
Q

What is the active layer of film X-ray sensors?

A

Emulsion layer; silver halide crystals

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33
Q

What happens to silver halide crystals when exposed to X-rays?

A

Become sensitised

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34
Q

What is film processing dependent on?

A 
Protected from light
Chemicals; liquids and vapours
Temp and time
Film washed and dried
Regular QA (sensitometry) checks
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35
Q

Explain the processing of film sensors

A

Developer: exposed green silver halide converts to black metallic silver; unexposed removed from plastic base
Fixer: black metallic silver fixed to plastic base
Wash: washes fixer off base

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36
Q

Define composite

A

2/+ materials put together w/ each contributing to overall properties

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37
Q

What are the main uses of composites?

A 
Filling material
FS
Endodontic post and cores
Luting agent
Indirect restorations
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38
Q

What are the 3 phases of direct composites?

A
  1. Organic matrix
  2. Inorganic filler
  3. Coupling agent
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39
Q

What is the function of the organic matrix of composites?

A

Monomer phase

Plastic monomer/resin material that polymerises to form a continuous phase, binding filler particles via coupling agent

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40
Q

What is the function of the inorganic filler phase of composites?

A

Reinforcing particles and/or fibres dispersed in matrix

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41
Q

What is the function of the coupling agent in composites?

A

Bonding agent promotes adhesion b/w filler and resin

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42
Q

Describe the organic matrix phase of composites

A

Chemically active component(s) which polymerise to form rigid polymeric material when cured
Monomer is viscous fluid which cures via FR, addition polymerisation

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43
Q

What monomers does the organic matrix of composites contain?

A

BisGMA: v viscous liquid
UDMA: alternative, less viscous

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44
Q

What does the high viscosity of the monomers in the organic matrix mean for the composite?

A

Makes unworkable

The addition fillers further inc. viscosity thus contain diluent monomers (viscosity controllers)

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45
Q

What additives are in the organic matrix of composites?

A

Hydroquinone: inhibitor for shelf life
Dihydroxyethyl-p-toluidine/benzoyl peroxide: activator/initiator RT cure
DHPT/camphorquinone: photo-initiator for LC
Filler: red. shrinkage
Pigments: iron oxide
UV stabilisers
Optical brighteners: fluorescence

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46
Q

What are the main 5 advantages to using fillers?

A
  1. Red. shrinking
  2. Red. coefficient thermal expansion
  3. Enhance modulus and strength (compressive) hardness
  4. May provide radio-opacity; identify on X-ray
  5. Control aesthetics; fluorescence, translucency, colour
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47
Q

Why is the refractive index of filler and resin important for composites?

A

Must match closely to avoid scattering light otherwise fill depth of cure will not be achieved on LC
Has major effect on colour

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48
Q

What are the main types of fillers?

A

Conventional/traditional: macro
Hybrid/small particle hybrid
Microfine

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49
Q

Describe traditional fillers

A

Macrofillers >1 microm
1st used ground quartz
Recently red. filler particle size <10microm
Poor finish: dull appearance due to filler particles protruding from resin surface

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50
Q

Describe microfine fillers

A

<1microm
Colloidal silica
Initially inc. viscosity but incorporation method improved
Can be polished: v smooth surface finish

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51
Q

What is the problem w/ microfine fillers?

A

V large SA of filler in contact w/ resin thus difficult to obtain high filler loading; large amount resin required to wet surfaces of filler particles
Max. filler loading 20% by volume

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52
Q

Explain the incorporation method of microfine fillers to ensure adequate filler loading

A

2 stage process

V high filler loaded material polymerised and ground to particles 10-40microm in size
These then used as fillers; have composite containing composite filler particles

Inc. loading to 50% by vol but < macrofilled

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53
Q

Describe hybrid fillers

A

Large filler particles (<10microm) and small amount colloidal silica (0.01-0.05microm) particles

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54
Q

Describe small particle hybrid fillers

A

Average particle size <1microm

Range 0.1-6.0microm

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55
Q

Advantages and disadvantages of hybrid fillers

A

Advantages:

  • favourable physical, mechanical, optical properties
  • improved wear resistance (cf macro)
  • surface morphology sup. to conventional, inf. to micro
  • radiopacity possible

Disadvantages:
- inc. surface roughness w/ T (cf micro), resin wears away

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56
Q

What is the advantage of a nanofilled composite?

A

Strength of hybrid

Polishing finish of micro

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57
Q

Compare the uses of microfilled and hybrid filled composites

A

Micro: ant. restorations due to lower filler loading; properties compromised
Hybrid: post. restorations due to higher filler loading; better mechanical properties

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58
Q

What is the advantage of using coupling agents?

A

Filler and resin must bond to have acceptable mechanical properties
Improved wear resistance of final restoration

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59
Q

Why must coupling agents be used?

A

Organic resin hydrophobic, filler hydrophilic (surface -OH) thus need agent to bond

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60
Q

How does silane coupling agent work?

A

Agent coated around filler particles (Silane treatment of filler)
Reacts w/ surface -OH filler via condensation

-OCH3 bonds -OH filler
Methacrylate group other end bonds organic resin

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61
Q

Why is a stable adhesive bond b/w filler and resin required?

A

No bond: stress transfer b/w filler and resin insufficient = creep, #, wear
No bond: crack initiation sites, grow w/ T = fatigue failure
Unstable bond: will # = disintegration

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62
Q

What are the 3 methods of curing composites?

A
  1. Heat: indirect, in/onlays
  2. RT: BP, dihydroxyethyl-p-toluidine
  3. LC: DHPT + camphorquinone
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63
Q

Discuss advantages and disadvantages of LC composite

A

Advantages

  • single component
  • less de-colouration
  • min. porosity as no mixing
  • virtually command set
  • rapid polymerisation
  • thin oxygen inhibited layer

Disadvantages

  • light sensitive during application
  • retina damage
  • limited cure depth; 2mm increments
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64
Q

At what range of wavelengths do visible light activated composites cure?

A

450-500nm

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65
Q

Describe the process for LC

A

Tip of light close to restoration surface; further away efficiency dec.
Tip not contaminated; red. efficiency
Cure for manufacturers recommended T, no less
Large restorations: no fanning, curing spots must overlap

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66
Q

Why do darker shades require longer curing time?

A

Pigments absorb more light thus must cure for longer

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67
Q

What are the 4 main types of LC units?

A
  1. Tungsten-Quartz-Halogen
  2. LED
  3. Plasma-Arc
  4. Argon Laser
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68
Q

Discuss Tungsten-Quartz-Halogen LC units

A 
Most common 
Tungsten filament
Radiates UV and white light 
400-500nm range; most photoinitatiors 
Cooling is critical; dec. bulb life
Quartz bulb life 30-50hrs
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69
Q

Discuss LED LC units

A 
Slimline
Cordless; rechargeable
Less lat. heat production (cf halogen)
Long lasting, low wattage
Narrow emission spectrum; 460-480nm
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70
Q

Discuss plasma arc LC units

A

Use xenon gas ionised to plasma
High intensity white light filtered (temp dec.) and allow emission blue light (400-500nm)
1-3s cure; rapid conversion of resin = high shrinkage)
Expensive

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71
Q

Discuss argon laser LC units

A 
High energy
Highest intensity 
Emit at single wavelength (490nm)
V expensive 
Warning signs required
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72
Q

What are the main advantages of composite restorations?

A
  1. Excellent aesthetics
  2. Less tooth tissue removed
  3. Command set (LC)
  4. Some cavity’s too small for amalgam (chip on incisal edge)
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73
Q

Name 6 disadvantages of composites

A
  1. Lining materials limited
  2. Setting inhibited w/ eugenol based materials
  3. Don’t adhere intrinsically to tooth tissue; acid-etch and adhesives required
  4. Incremental placement, LC: 3x longer cf amalgam to place
  5. Caries tends to progress more rapidly due to shrinkage
  6. Stick to instruments problems w/ marginal adaptation
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74
Q

Why is shrinkage a problem for composite restorations?

A

2-3% by vol
Problems for marginal adaptation
Breakdown of bonds to tooth tissues
Can result in recurrent caries

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75
Q

Discuss water uptake as a disadvantage of composites

A

Glass filler adsorbs water onto its surface, amount depends on resin content and quality of bonds
Causes
- hydrolytic breakdown of resin-filler bond
- unreacted monomer and soluble fractions release leaving space
- water fills pores/air voids in cured composite (due to mixing/placement)

Affects wear resistance and colour stability (staining)

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76
Q

Discuss staining of composites

A

Marginal: gap b/w restoration and tooth; debris penetrates -> staining
Surface: roughness of composite causes debris to become trapped = staining
Bulk: 2 paste amine cured systems

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77
Q

Why is wear a problem for composites?

A

Abrasive, fatigue, corrosive

W/ T resin matrix wears, filler particles protrude through surface giving dull appearance

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78
Q

Why is biocompatibility an issue for composites?

A

Composite components and breakdown products released
Uncared resin can lead to
- cytotoxicity and delayed hypersensitivity from eluted materials
- oestrogenic effects

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79
Q

Discuss the oxygen inhibition layer of composites

A

Oxygen inhibits resin curing thus reliving in sticky resin surface

Benefit is incremental placement, well bonded material
Problems is surface of final increment will be sticky
Solution
- matrix strip
- overfill and polish
- apply bonding agent

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80
Q

Discuss silorane

A 
New composite material 
Polymerisation shrinkage <1%
Lower shrinkage stress/strain
Lower H2O absorption 
Mechanical properties 'within range' of other composites
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81
Q

Discuss bulk fill

A

New composite material
1-step placement, no additional capping layer
Excellent adaptation w/o additional expensive dispersing devices
Stress relief enables up to 5mm depth cure
Excellent handling and sculptability

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82
Q

What are the advantages to using adhesives?

A

Better aesthetics
Conservation of tooth tissue
Reinforcement of weak tooth structure
Red. marginal leakage

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83
Q

What are the ideal requirements of an adhesive?

A

Provide high bond strength to enamel and dentine
Immediate and durable bond
Prevent ingress of bacteria
Safe and simple to use

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84
Q

Discuss the problems encountered w/ bonding composite to enamel

A

Composites have no intrinsic adhesion to tooth tissues
Composites non-polar; Enamel hydrophilic
Enamel surface tension < adhesive resin; prevent perfect wetting thus resin won’t flow/cover enamel
Pellicle layer even lower surface energy, prevent perfect wetting

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85
Q

How are the problems encountered when bonding composites to enamel combated?

A

Pellicle removed, surface etched to raise surface energy
Ideal situation: surface energy liquid just < surface energy solid

Acid-etch technique results in micromechanical retention (intimate bonding b/w resin and enamel)
30-50% (37%) phosphoric acid applied, acid-base reaction initiated, dissolves surface HA, lose enamel prisms

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86
Q

What are the main effects of the acid-etch technique?

A

Removal of pellicle and contaminants results in

  • inc. surface roughness; bonding area inc.
  • inc. surface energy
  • improved wettability
  • opens inner prism areas for interlocking tag formation
  • inc. area of contact and micromechanical bonding = adhesion
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87
Q

Describe application of resin after acid-etch bond technique

A

Recommended to apply low viscosity resin prior to placement of composite
Resin applied to dry/well etched enamel surface
Flows into etched enamel prisms forming resin tags

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88
Q

Why is it important to have adhesion b/w resin and dentine?

A

Retain restoration in cavity; dentine hydrophilic, resin hydrophobic
Eliminate marginal/internal gaps to prevent bacterial microleakage

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89
Q

What problems are faced when bonding composite to dentine?

A

When cut, fluid pumped through dentine tubules giving wet surface
Inorganic HA crystals broken, collagen stretched, torn and smeared over surface giving smear layer

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90
Q

What is the smear layer?

A

Layer of denatured collagen and debris covering surface and weakly bound to dentine
Contaminated w/ bacteria (caries) and cutting debris

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91
Q

What is required for strong bonding of resin to dentine?

A

Complete removal of smear layer
This opens dentine tubules thus exposed to bacteria and irritants therefore adhesive resin must act as effective seal to seal tubules

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92
Q

What are the 3 essential components to dentine bonding agents?

A
  1. Conditioner (etch)
  2. Coupling agent/primer (prime)
  3. Sealer (bond)
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93
Q

Describe dentine conditioner

A

Acid solution; stronger, more pronounced effect
Remove/modify smear layer; acid-base reaction w/ HA
Rinsed w/ water
Demineralised dentine surface left

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94
Q

Describe the dentine coupling agent

A

Acts as adhesive bonding dentine to resin

Has bi-functional molecule such as HEMA

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95
Q

What must the dentine coupling agent do to achieve strong bonding?

A

Penetrate and saturate dentine tubules to reasonable depth thus must be dissolved in solvent (ethanol, acetone)
Seeks out and displaces water

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96
Q

Describe the dentine sealer

A

Unfilled bisGMA or UDMA and may include primers to wet dentine
Make dentine more hydrophobic
LC

Recent: mix. BisGMA and UDMA; improve adaptation of sealer to dentine surface

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97
Q

What is the hybrid layer of dentine?

A

Interpenetrating layer of dentine and resin
Formed by components of bonding agent penetrating dentinal collagen forming long resin tags in demineralised dentine tubules and strong micromechanical bonds

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98
Q

Discuss the biocompatibility of dentine bonding agents

A

Excessive desiccation of dentine can cause post operative pulpal sensitivity and a poor bond

If bond fails can cause pulpal inflammation due to bacterial leakage

Allergic reaction or contact dermatitis can by caused by regular direct contact with primer/adhesive due to HEMA

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99
Q

What are some of the causes of adhesive bond breakdown and what can this result in?

A

Causes

  • polymerisation shrinkage
  • differential thermal expansion and contraction
  • internal stresses from occlusal loading
  • chemical attack; hydrolysis

Result

  • bacteria and debris in cavity margins
  • marginal staining
  • pulpal sensitivity
  • lost restoration
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100
Q

Discuss different tooth surfaces as habitats for microbial flora

A

Approximal and gingival crevice: protect from adverse conditions, support diverse community; anaerobic, gingival crevice bathed in gingival crevicular fluid

Smooth: exposed to environmental forces; colonised by limited no. well adapted bacterial species; properties differ whether surface facing B/L

Pits and fissures: protected from environment; largest communities and most disease

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101
Q

Discuss mucosal surfaces in mouth as habitat for microorganisms

A

Papillary surfaces on dorsum: microorganisms that would otherwise be removed by mastication and saliva

Tongue crypts: low redox potential; may act as reservoir for gram- anaerobes implicated in periodontal disease

Both non/keratinised stratified squamous epithelium may affect distribution

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102
Q

Discuss how saliva can affect microorganism growth

A

Flow, ion content influence caries susceptibility

Glycoproteins:

  • influence aggregation and adhesion of bacterial to surfaces
  • interact w/ other components and immune defences
  • primary source nutrients for normal microflora

Urea, AA: metabolism inc. pH

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103
Q

Discuss how GCF can alter microflora growth

A

Serum components reach mouth via GCF through junction alone epithelium of gingivae

Influence ecology by physical removal of non-adherent microbial cells

Nutrient source
Immune system: regulate microflora of gingival crevice in health and disease

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104
Q

Describe factors of non-specific immunity in the mouth

A
  1. Physical removal: saliva, GCF, swallowing
  2. Lysozyme: hydrolysed peptidoglycan in CWs
  3. Lactoferrin: iron-binding glycoprotein
  4. Salivary peroxidase enzyme system
  5. Antimicrobial peptides: histidine-rich peptides regulate
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105
Q

Describe factors of specific immunity in the mouth

A

Intra-epithelial lymphocytes, Langerhans cells, IgA mucosa: regulate Ag
Secretory IgA: agglutinates bacteria, modulates enzyme activity and inhibits adherence to B epithelium and enamel
GCF: IgA, IgM, IgG, complement, neutrophils
Ab production stim. by bacterial Ag at gingival margin or on oral mucosa

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106
Q

Discuss Strep. mutans in relation to dental caries

A

Gram-+ cocci
Isolated from all sites in mouth
Many produce EC polysaccharides associated w/ plaque formation

Regularly isolated from dental plaque, prevalence low on sound enamel
Primary aetiology of enamel caries in children, root caries in elderly (recession)

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107
Q

Discuss gram-+ rods and filaments in relation to dental caries/plaque

A

Facultative and obligate anaerobes

Actinomyces

  • major portion dental plaque esp. approximal and gingival crevice
  • no. inc. w/ gingivitis, associated w/ root surface caries

Lactobacillus p

  • proportions and prevalence inc. w/ advanced caries of enamel and root surface
  • highly acidogenic
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108
Q

Discuss gram negative rods in relation to dental plaque and caries

A

AA: aggressive periodontitis

Porphyromonas gingivalis: subgingival sites (periodontal pockets), highly virulent

Prevotella intermedia: subgingival plaque, some associated w/ periodontal disease and abscesses

Fusobacterium: normal gingival crevice, periodontal pockets

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109
Q

Most important and prevalent fungi in mouth?

A

Candida albicans

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110
Q

Discuss presence of viruses in the mouth

A

Herpes simplex: most common
Hepatitis, HIV: present in saliva of asymptomatic pt
Coxsackie and papilloma: lesions, cancer

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111
Q

Define occlusion

A

Static relationship b/w 1/+ max. teeth and 1/+ mand. teeth

Teeth in contact w/ each other (when clenched)

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112
Q

Ortho definition of occlusion

A

Incisor relationship

Class I: L incisors occlude w/ cingulum plateau U incisors
Class II: L incisors occlude post. cingulum plateau Us
- div 1: U1s proclined or average inclination, overjet inc.; bugs bunny
- div 2: U1s retroclined, min./slight inc. overjet
Class III: L incisors occlude ant. cingulum plateau Us; overjet red./reversed

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113
Q

What is the maximum intercuspation position?

A

Position w/ most tooth-tooth contact for that individual’s occlusion

Importance: restorations must harmonise w/ existing occlusion (conformative occlusion)

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114
Q

Define articulation

A

Dynamic gliding contacts b/w 1/+ max. teeth and 1/+ mand. teeth

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115
Q

What is Posselt’s envelope?

A

Diagram of sagittal movement of mandible

Resting, intercuspal, incisal contact, max. protrusion, max. opening, habitual closing

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116
Q

How is dynamic articulation classified?

A

Canine guidance: V and H overlap of 3s causes post. teeth working side to disengage during lat. movement

Group function: multiple contacts b/w teeth during lat. movement

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117
Q

Why can group function articulation be problematic?

A

Lat. loading can # thin walls of restorations

Use composite to build up ramp on 3s to keep ICP and restore canine guidance

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118
Q

Explain working side and non-working side articulation interference

A

Working side = side moving mandible to

Working side interference: contact b/w UandL post. teeth on same side of arch as moving mandible to

Non-working side: contact b/w UandL post. teeth on opposite side of arch from direction of mandible movement

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119
Q

Define plaque

A

General term for complex microbial community embedded in matrix of salivary and bacterial components (biofilm) and found on teeth

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120
Q

Outline the development of plaque

A
  1. Acquired enamel pellicle; deposited on clean surface, complete in 2hrs; proteins, glycoproteins, lipids from bacteria, saliva, GCF
  2. Pioneering species adhere; to pellicle; passive transport of bacteria attachment through adherins: Strep. oralis, mitis, sanguinis; Actinomyces spp.
  3. Pioneering species multiply; form confluent layer; utilise salivary glycoproteins, cleave IgA via IgA proteases
    - co-aggregation occurs; cell-cell interactions result in distinctly different bacterial species becoming predetermined partners
  4. Accumulated growth;
    - dec. O2 tension
    - growth of anaerobes
    - inc. diversity
  5. Maturity
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121
Q

What 4 things is accumulation of plaque dependent on?

A
  1. Adhesion
  2. Growth
  3. Removal via physical forces
  4. Plaque interactions
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122
Q

Describe the structure of mature dental plaque

A

Tooth surface

Acquired pellicle

Early colonisers: Strep. sanguinis, oralis, mitis; Actinomyces so

Fusobacterium nucleatum

Late colonisers: Porphyromonas gingivalis

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123
Q

Discuss function of establish plaque from bacterial perspective

A

Microbial homeostasis; maintenance of stable microflora in variable environment due to dynamic balance

  • enhanced catabolism endogenous nutrients
  • protection from stressful environment; maintain favourable local environment
  • persist and grow over wider habitat range
  • display synergy in nutrient recycling
  • metabolic efficiency inc.
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124
Q

Describe function of dental plaque from host perspective

A

Exclusion of exogenous organisms from entering and becoming established in mouth
Bacterial
- competition for adhesion R sites
- competition for nutrients and co-factors
- production inhibitory substances; acids, H2O2

Host
- immunity and innate defence; lysozyme (bacterial lysis), lactoferrin (iron sequestration), peroxidases (glycolysis inhibition)

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125
Q

What is the drop in pH after sugar intake dependent on?

A 
Type, amount carb available
Bacteria present
Salivary composition and flow
Other food ingested
Thickness and age plaque
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126
Q

Discuss resting plaque pH and account for differences in it

A

Constant within individual, differences within groups
Caries inactive pH ~6.5-7.0

Differences

  • bacterial composition affects metabolic properties
  • storage firm carb -> energy source when fasting
  • cariogenic bacteria prod. acids from storage carbs
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127
Q

Discuss the fluctuation in plaque pH

A

Alkalinisation: acid diffusion, buffering, alkali from bacteria metabolism
Alkali generation: ammonia and/or CO2 end products
- ureolysis: S. salivarius; urease to hydrolyse urea in saliva
- Strickland: peptostreptococci; oxidise proline in AAs and red. protons in plaque
- arginine deiminase system: S. rattus; arginine deiminase to catabolise arginine in diet to from ammonia

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128
Q

Discuss the ecological plaque hypothesis

A

Beginning: low level S. mutans and lactobacilli (resident) other bacteria prod. acid, stability in plaque composition
Change in environment (freq. sugar/fermentable carbs) shift balance in microflora
pH decrease, aciduric bacteria survive favouring growth SM and lactobacilli (cariogenic) thus leading to caries

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129
Q

Discuss metabolism of carbs in relation to plaque

A

Glycolysis: glc->pyruvate
Pyruvate fermented by plaque bacteria to lactate
Homofermentative bacteria >90% lactic acid
Heterofermentative bacteria formic, propionic, acetic, succinc acids

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130
Q

Discuss the 4 concepts in cariogenic bacteria that allow for their survival

A
  1. Acidogenicity: rapidly prod. acid from fermentable carbs
  2. Acidouricity: ability to survive and continue prod. acid in acidic pH
  3. Prod. EC polysaccharides from sucrose to aid tooth adherence and build up of bacterial deposits
  4. Prod. IC polysaccharides as storage components to prolong acid formation and acidic pH (even when carb depleted)
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131
Q

Discuss IC polysaccharides in dental plaque

A

Storage form carbs: glycogen-amylopectin
Energy and acid prod. when dietary carb depleted

Acidogenicity: caries-prone plaque prolonged prod. acid from storage IPS
Aciduricity: IPS -> energy for ATPase, drives protons out cell -> adapt low pH

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132
Q

Discuss EC polysaccharides in dental plaque

A

Before sucrose enters cell <10% -> glucans and fructans

  • diffuse into surrounding cell
  • remain associated w/ cell

Glucans

  • major component inter-bacterial matrix
  • barrier to outward diffusion acid from plaque
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133
Q

Define primary, secondary, residual, rampant and hidden caries

A

Primary: lesion on unrestored tooth
Secondary: lesion adjacent to filling
Residual: demineralised tissue left behind before filling placed
Rampant: multiple active carious lesions in same pt
Hidden: dentine caries, only detectable radiographically

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134
Q

Define active and arrested caries

A

Active: considered to be progressing
Arrested: no longer progressing

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135
Q

Define white spot and brown spot lesion

A

White spot: first sign visible by naked eye w/ strong white light
Brown spot: inactive white spot discoloured by uptake of dye

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136
Q

Functions of saliva

A 
Neutralise acids
Prevent demineralisation/enhance remineralisation
Recycle ingested F to mouth
Discourage bacteria growth
Proteins sustain enamel surface 
Protective, coating, lubrication
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137
Q

Discuss importance of Ca and PO in saliva

A

Saliva supersaturated wrt Ca, P.O.
Prevent dissolution and enable remineralisation of initial carious lesions

However, when pH drop, proteins change conformation and release Ca leading to possibility of calcium phosphate (calculus) precipitation

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138
Q

Discuss smart bioactive molecules in saliva

A

Modify supersaturation by making potentially supersaturated wrt Ca, PO
Prevent unwanted precipitation by binding excess Ca
Release Ca when pH drop below critical value to prevent dissolution

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139
Q

Describe Stephan curve

A

Graph plots pH against time
Shows resting plaque pH, how long takes saliva to return to normal after sugar intake
Usually 30-40 mins
W/ caries pH starts lower (bacteria prod. acid), drops lower and takes longer to return to resting value

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140
Q

What is the critical pH?

A

5.5

pH at which saliva is no longer supersaturated wrt Ca, PO this dissolution takes place; net loss of enamel

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141
Q

Define acid-base cement

A

Formed on mixing powder and liquid, which, through acid-base reaction prod. solid matrix that binds mass together

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142
Q

Discuss ideal properties of acid-base cement

A 
Non-toxic, non-irritant
Insoluble in oral fluids/intaken fluids
Thermally, chemically, electrically insulating 
Adhesive to tooth
Easily manipulated 
Adequate mechanical properties
Good optical properties
Appropriate rheological properties
Appropriate thermal expansion coefficient
Radio-opaque
Bacteriostatic and obtundent
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143
Q

Discuss general setting of acid-base cements

A

Acidic liquid + basic/amphoteric oxide powder -> salt-cement matrix + water

Setting is never complete
Set cement consists of cored-structure, unreacted particles act as filler; inc. strength set cement

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144
Q

3 factors affecting setting of acid-base cements

A

Particle size: smaller size > specific surface area and faster set

Powder:liquid ratio: inc. powder = faster set

Temp: inc. temp = inc. rate; setting is exothermic thus may further accelerate reaction

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145
Q

How can acid-base cements be classified?

A 
Type
Application
Powder
Liquid
Bonding
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146
Q

Classify acid-base cements by type

A 
Zinc phosphate
Zinc polycarboxylate
Zinc oxide/eugenol (ZOE)
Glass ionomer cements (GICs)
Calcium hydroxide
Ethoxybenzoic acid (EBAs)
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147
Q

3 classifications of acid-base cement by application

A

I: luting
II: restorative or lining
III: lining or base

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148
Q

Classify acid-base cements by chemical bonding

A

Phosphate bonded: zinc phosphate
Polycarboxylate: zinc polycarboxylate, GICs
Phenolate: CaOH, ZOE, EBA

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149
Q

Classify acid-base cements by liquid base

A

Water based: zinc phosphate, zinc polycarboxylate, GIC

Oil based: CaOH, ZOE, EBA

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150
Q

Classify acid-base cement by powder

A

Zinc oxide: zinc polycarboxylate, zinc phosphate, ZOE, CaOH2, EBA
Ion leachable glass: GIC

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151
Q

Discuss composition of zinc phosphate acid-base cement

A

Powder

  • main component ZnO (90%)
  • MgO (10%) inc. strength, maintain whiteness
  • Al2O3, SiO2 mechanical reinforcement
  • SnF2 short-term F release
  • ZnO, MgO heat treated >1000 to dec. reactivity

Liquid

  • primary phosphoric acid (45.3-63.2%)
  • Al3+, Zn2+ cations partially neutralise to slow setting reaction
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152
Q

Outline setting of zinc phosphate

A

Complex, 2 stages

  • ZnO + H3PO4 -> Zn(H2PO4)2 + H2O (unbound)
  • ZnO + Zn(H2PO4) + 2H2O -> Zn3(PO4)2*4H2O (bound)

Sensitive to water contamination during setting

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153
Q

Discuss advantages and disadvantages of zinc phosphate

A

Advantages

  • adequate strength
  • sharp set
  • rapid hardening; most strength within 3h
  • fairly good retentive properties: mechanical interlocking
  • good thermal insulation
  • cheap
  • SnF2/tannin fluoride have F release

Disadvantages

  • low initial pH; enamel dissolution, pulpal irritation
  • SnF containing are weaker
  • slow to neutralise
  • brittle: tensile strength 5-7MPa
  • low acidic solubility
  • linear setting shrinkage 0.5%
  • no chemical adhesion
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154
Q

Discuss properties of zinc phosphate

A

Depend on power:liquid especially for strength

Compressive strength 40-140MPa

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155
Q

Uses for zinc phosphate cement

A

Primary: luting for restorations and ortho due to strength
Secondary: thermal insulating base, temp. restorative

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156
Q

Discuss composition of zinc carboxylate cement

A

Powder

  • main: ZnO
  • other; MgO, SnO, Al2O3, SiO2 (mechanical reinforcement)
  • ZnO, MgO heat treated dec. reactivity
  • Bismuth salts modify set
  • SnF2/tannin flurodie: F source, improve mixing, inc. strength

Liquid

  • primary; polyacrylic acid (PAA) (30-45%)
  • copolymers w/ other unsaturated carboxylic acids
  • PAA may be freeze dried, converted to powder, mixed w/ other powder components; liquid will then be H2O
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157
Q

Discuss setting of zinc polycarboxylate

A

Complex
Min reaction b/w ZnO and -COOH of PAA

Freshly mixed cement is pseudoplastic (shear thinning)
Inter and intramolecular crosslinks formed

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158
Q

Discuss dis/advantages of zinc polycarboxylate

A

Advantages

  • chemical adhesion: COO of PAA binds to HA through chelation of Ca2+
  • low irritancy, despite low pH rapid neutralisation
  • tensile strength, H2O solubility similar ZnPO, less acid soluble
  • strength not as dependent on optimum powder:liquid
  • strength attained quickly; 75% in 15min
  • SnF/tannin fluoride containing transient F release

Disadvantages

  • lower compressive strength (55-85MPa)
  • short working time
  • not necessarily adhesive to all metal or porcelain restorations
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159
Q

Uses of zinc polycarboxylate

A

Primary

  • luting (adhesive potential)
  • thermal insulating base (low irritancy)

Secondary

  • luting ortho bands
  • intermediate and temporary restorations
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160
Q

Discuss composition of conventional GICs

A

Powder

  • ion leachable (ionomer) glass
  • basic: SiO2, Al2O3, CaF2
  • other: AlPO4, Na3AlF6, AlF3, NaF
  • Sr2+, Ba2+, La3+ radiopactiy
  • SiO2/Al2O3 ratio governs reactivity

Liquid

  • polyacrylic acid 50% aqueous solution
  • or copolymer of acrylic and itaconic acid
  • or other carboxylic acids (maleic)
  • tartaric acid 10%

Both acids can be freeze dried, mixed w/ powder; liquid just H2O

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161
Q

Discuss importance of tartaric acid in GICs

A

Tartaric acid complexes are stable up to set pH
They ‘hold’ cement forming ions (inc. working time) until acid is partially neutralised
Ions released giving sharp set

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162
Q

3 stages of GIC setting

A

Dissolution
Gelation
Final maturation

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163
Q

Discuss dissolution of GICs

A

H+ from polyacid attack glass liberating Ca2+, Al3+
- other ions released Na+, F-
Released silicon forms Si(OH)4
Ca, Al in form of complexes w/ F or tartaric acid

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164
Q

Discuss gelation stage of GIC setting

A

Set occurs by poly chain entanglement and cross linking of chains by Ca2+ (initial set) and Al3+ (final set)
Form hydrated Ca, Al polyacrylates

Ca2+: mobile ion, weak bonding, H2O soluble
Al3+: less mobile, strong bond, insoluble polyacrylate

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165
Q

Discuss final maturation of GIC setting

A

Ratio bound:unbound H2O inc.
Strength inc.
Take up to 24h; GIC needs to be protected immediately after placement

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166
Q

Importance of water balance in GICs

A

Early H2O exposure: dissolution of reactive components (cross linking ions)

Dehydration: loss of water critical for continuation of setting

Both: GIC w/ poor properties

Thus, cement must be protected immediately after placing
Final polish after 24h

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167
Q

Discuss chemical bonding in GIC

A

Condition tooth surface w/ PAA (10-30%)
- removes smear layer, makes surface chemically active
Chelation of Ca2+ (from HA) w/ COO- (from PAA); strong ionic bond
H+ bonding w/ -NH2 (collagen)
Ion exchange b/w tooth and cement
Ion rich interfacial layer formed

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168
Q

Discuss how GIC can inhibit caries

A

Ion release
Fluoride
- initial high level from exposed glass particles
- long term low level from deeper in matrix (diffusion controlled)
- F uptake by dentine and enamel, inhibit demineralisation
- F recharge and re-release

Na, Ca released
Involves continuing ion exchange cement/tooth/saliva
Ca, Sr, P.O. diffusion transfer to enamel/dentine
Possible remineralisation

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169
Q

Discuss biocompatibility of GIC

A

Bioactive
Low irritant despite low pH
H+ movement constrained by high MWt polymeric anion
Restricts diffusion down dentinal tubules

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170
Q

Discuss dis/advantages of GICs

A

Advantages

  • aesthetics; depends on glass composition, changes during maturation
  • thermal expansion coefficient similar to tooth
  • selfhealing, repairable; uptake Ca, PO from saliva
  • potential to remineralise
  • no shrinkage, no exothermic, no free monomer
  • chemical bond
  • long term F release and uptake

Disadvantages

  • weaker cf composite, amalgam but inc. w/ age (150MPa)
  • poor wear resistance at early stage, inc. w/ age
  • short working time, long setting time
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171
Q

Uses of GICs

A

Ant. restoration
W/ composite in sandwich technique
Tunnel restorations
Luting and repair materials for crown/bridge
Cavity lining, base under composite and amalgam
Repair erosion lesions, FS

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172
Q

Discuss high viscosity GICs

A 
Originally designed for atraumatic restorative technique 
Finer particle size powder
High MWt acids
Compressive strength 2-300MPa
High F release

Chemfil Rock; Zn, PO containing faster strength build up

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173
Q

Discuss composition cermets

A

Powder

  • metal (usually silver) fused to GIC powder then ground
  • or metal powder mixed w/ GIC powder
  • ~5% titanium dioxide improves colour

Liquid: conventional GIC

  • 50% PAA
  • 10% tartaric acid
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174
Q

Discuss properties and uses of cermets

A

Properties

  • more abrasion resistant, less brittle cf GIC
  • red. F release, bond strength
  • radiopaque
  • difficult to handle

Uses

  • cermet/composite laminate technique
  • lining for amalgam
  • repair restoratives
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175
Q

Discuss composition resin modified GIC

A

Powder: ionomer glass, photosensitiser

Liquid

  • PAA, tartaric acid
  • H2O compatible vinyl monomer (usually HEMA)
  • or PAA w/ pendant methacrylate groups
  • photo-initiator system
  • can contain some BisGMA
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176
Q

Discuss dis/advantages of RMGICs

A

Advantages

  • less soluble
  • less brittle; tensile strength ~20MPa
  • polished immediately
  • F release similar/higher
  • adhesion to tooth
  • compressive strength ~105-170MPa
  • longer working time, rapid set

Disadvantages

  • HEMA slows acid-base reaction
  • DoC < composites; red. light transmission of filler
  • polymerisation exotherm > composites
  • polymerisation shrinkage
  • swell in H2O after cure as PHEMA is hydrogel
  • if not photocured quickly properties altered
  • unpolymerised HEMA cytotoxic
  • stain
  • HEMA, BisGMA, PAA separate in bottle
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177
Q

Uses of RMGIC

A 
Cavity lining
In GIC-composite laminate technique 
Ant. restorative
Restorative in deciduous teeth
Luting cement
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178
Q

Discuss composition of polyacid modified composites/compomers

A

Powder

  • BisGMA/UDMA + visible light curing system
  • acidic monomer; bifunctional monomer w/ pendant -COOH
  • ion leachable fluoroaluminosilicate glass filler + conventional fillers
  • hydrophilic monomers aid H2O absorption and F release
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179
Q

Discuss properties of PAMC/compomers

A

Good handling, adapt easily cavity walls, don’t slump
Require dentine BA
Shrinkage similar to composites
Level H2O uptake similar composite but rate faster
Inf. mechanical properties cf composites

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180
Q

Uses PAMC/compomers

A 
Low stress situations
Proximal and abrasion cavities
Restorations primary teeth
Long term temporary restorations permanent teeth
Recently, luting cement
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181
Q

Discuss giomers

A

Composite resin + pre-reacted GI particles as filler
Have F release, recharge of F w/ sup. properties of composite

Restorative, luting, FS

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182
Q

Discuss new development being made in acids for GIC

A

Polyvinyl phosphoric acid

More reactive
Improved strength, moisture resistance
Less acid soluble

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183
Q

Requirements for caries detection

A

Sharp eyes, magnification: eye test, loupes
Good illumination: operating light, fibre optics
Clean tooth
Examine wet and dry
Round/ball-ended explorers- not sharp, could cavitate
Time

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184
Q

Define classifications of caries lesion

A

1: cavity pits/fissures on O surface post. teeth/lingual U incisors
2: cavity proximal surface post. teeth
3: cavity proximal surface ant. teeth
4: cavity proximal surface ant. teeth involving incisal edge
5: cavity cervical 1/3 tooth

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185
Q

Discuss special investigations into caries lesions

A

X-rays: BWs

Sensibility testing (response to stimuli - test vitality)

  • temp.
  • electrical pulp tester
  • text cavity (drill)
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186
Q

Discuss sequence for accessing caries lesions

A

Diagnosis

  • detect caries
  • determine activity
  • determine need for treatment

If operative

  • gain access
  • identify caries/sound interface
  • excavate caries
  • determine most appropriate material
  • modify cavity
  • restore
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187
Q

Discuss the aims and equipment used for enamel preparation for caries lesions

A

Aims

  • gain access to fill extent deeper carious dentine
  • remove demineralised/weakened carious enamel
  • create sound peripheral machine to seal w/ restorative

Equipment

  • air-rotor; high speed >250000rpm
  • diamond bur; strong, cut through enamel
  • hand chisels
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188
Q

Define anatomical extent ands histological depth of carious lesion

A

Anatomical extent: lat. extent of lesion from EDJ across overlying pulp

Histological depth: collagen and mineral of caries-infected vs caries-affected vs sound dentine

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189
Q

Discuss sequence and equipment used for dentine removal

A

Sequence

  • identify caries infected dentine w/ probe (dark brown, soft, wet)
  • identify peripheral extent to EDJ
  • excavate peripherally first (clear EDJ)
  • move towards pulp; anatomically and histologically

Equipment

  • slow speed; <5000rpm, conservative, precise
  • rose head steel bur; use large head to get uniform cut through dentine
  • hand excavators
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190
Q

Define cavity retention and cavity resistance

A

Retention: resist displacement in direction of insertion

Resistance: resist displacement in any other direction

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191
Q

Compare stepwise and atraumatic restorative technique

A

Stepwise

  • access
  • clear EDJ
  • leave deeper caries over pulp
  • place Ca(OH)2 lining
  • provisional zinc polycarboxylate restoration
  • re-access 6-9mns (tertiary dentine formed)
  • remove affected (but arrested) dentine
  • definitive restoration

ART

  • access
  • clear EDJ
  • leave deeper caries over pulp
  • provisional GI restoration
  • leave or laminate/sandwich restoration (over GI)
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192
Q

Define dentine-pulp complex

A

Dynamic tissue that responds to mechanical, bacterial and chemical stimuli as functional unit

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193
Q

Compare pulp and dentine

A

Common ancestry (dental papilla), developmentally closely interrelated but no chemical similarities

Collagen: dentine T1, pulp T1,3,5
Peripheral dentine has no basement membrane so no T4
No fibronectin in dentine

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194
Q

Importance of dentine being a living tissue

A

Pulpal blood vessels supply nutrients, structural materials
Pulpal nerves mediate sensitivity

Injury/caries starts inflammatory response can progress to pulp death
Dentine becomes inert, unable to respond or repair self
Tooth may fracture thus restorative strategies depend on dentine vitality

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195
Q

Discuss response of dentine to caries and treatment

A

If mild, odontoblasts stim./up-regulated to secrete reactionary 3ry dentine
If progresses and becomes extensive odontoblasts may die
Can be replaced by odontoblast-like cells that secrete reparative 3ry dentine

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196
Q

Compare reactionary dentinogenesis and reparative dentinogenesis

A

Reactionary: req. stim. of existing odontoblasts

Reparative: req. recruitment progenitor cells from cell rich layer of pulpal tissue

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197
Q

How does dentine respond to cavity preparation?

A

Is injury; burs produce vibrations causing in/outward fluid shifts
Shifts continue in both directions at various stages of cavity preparation
Application of DMs also causes fluid shifts

Results in barrage of hydrodynamic stimuli across dentine into pulp causing pain if no LA

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198
Q

What is a consequence of the fluid shifts during cavity preparation?

A

If release enough NT can cause local pulpal neurogenic inflammation under irritated tubules cause change in pulpal blood flow

Displacement of odontoblasts into tubules disrupts Internal cytoskeleton can lead to cell death

  • replaced by new cells over few days
  • if dentine not sealed following preparation microleakage within restoration
  • acute pulpal reactions progress to chronic stage due to microorganisms and products
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199
Q

What is the problem w/ current equipment used for assessing caries?

A

No non-invasive tools to assess pathological condition or severity of inflammation within pulp

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200
Q

What factors affect pulp healing?

A 
Drill speed
Use of coolant
Operator pressure
Extent of cavity preparation
Unnecessary iatrogenic removal of dentine
Extensive, prolonged use of acid-etch
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201
Q

Discuss pulp capping

A

Direct; w/o stepwise cavitation

  • no pulpal tissue to the coronal of the exposure due to difficulty in reactionary dentine formation which can lead to necrosis and failure
  • only through non-infected dentine and when bacterial-tight seal can be made

Indirect; w/ stepwise cavitation

  • layer infected dentine deliberate left over pulp
  • difficulty knowing how rapid carious process is
  • how much 3ry dentine formed
  • when to stop excavating
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202
Q

How can tissue engineering aid pulp-dentine complex?

A

Application of advanced biological systems w/ therapeutic agents that control inflammatory response of pulp-dentine complex while inducing remineralisation of dentine

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203
Q

Define cavity liner

A

Permanent, intermediate restorative material lining cavity applied before placement of restorative

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204
Q

3 types of cavity liner

A

Varnish
Cavity liner
Cavity base

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205
Q

What factors impact cavity liner choice?

A 
Position
Size and depth
Condition of tissues
OH
Restorative being used
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206
Q

Role of cavity liners

A

To be

  • protective
  • palliative; relieve pain
  • therapeutic to vital dentine
  • barrier to penetration through tubules

Protect pulp

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207
Q

Discuss cavity varnishes

A 
Coat layer painted on cut surface; 2-5microm
Seal dentine
Red. diffusion through tubules
- barrier to penetration of chemicals 
Dec. microleakage
No strengthening property
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208
Q

Composition of cavity varnishes

A

Natural resins; copal
Synthetic resins; polystyrene
Solvent; alcohol, acetone, ether
Some: Ca(OH)2 and/or ZnO

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209
Q

Discuss suspension liners

A

Non-setting Ca(OH)2
- Ca(OH)2 suspension in H2O
20-25microm thick layer
Methyl or ethyl cellulose can be added for strength

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210
Q

Discuss cavity liner

A 
Thin coat <0.5mm
Seals exposed dentine
Promotes health of pulp
- adheres to tooth structure
- antibacterial
Materials: Ca(OH)2, ZOE, ZnO non-eugenol
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211
Q

Discuss cavity base materials

A 
Thick mix, placed in bulk
Thick layer >0.75mm
Dentine replacement
Min. bulk of restorative 
Block out undercuts
Higher strength 
Insulating
Materials
- reinforced ZOE
- visible light cured resins
- zinc phosphate and polycarboxylate 
- GI and RMGIC
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212
Q

Composition of Ca(OH)2 based cements

A

Paste 1: base

  • salicylate ester 40%: butylene glycol disalicylate
  • fillers: TiO2, CaSO4, BaSO4

Paste 2: catalyst

  • Ca(OH)2 50%
  • ZnO 10%
  • plasticiser 40%: toluene sulphonamide, zinc stearate
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213
Q

Discuss setting reaction of Ca(OH)2 based cements

A

Acid-base reaction

Disalicylate reaches w/ Ca(OH)2 and ZnO to form chelate-calcium disalicylate

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214
Q

Discuss handling of Ca(OH)2 cements

A

= vol. 2 pastes dispensed on oil-resistant paper pad
Mix time 5-30s; work 30-60s; set 1-2min
High alkaline pH (fresh up to 12), lower when set

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215
Q

Discuss dis/advantages of Ca(OH)2 cements

A

Advantages

  • easy mix, handle
  • rapid hardening in thin layers
  • moisture accelerates set
  • good seal
  • pH 9-12: neutralise acid materials; zinc phosphate
  • antibacterial
  • stim 2yr dentine: contact w/ pulp causes necrosis layer that calcifies
  • compatible w/ composite

Disadvantages

  • low strength: compressive 20MPa
  • weakened by moisture
  • dissolve completely in acid where marginal leakage occurs
  • undergo plastic deformation at mouth temp.
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216
Q

Discuss uses of Ca(OH)2 cements

A

Cavity liners: esp. deep cavities, pulp capping
W/ composites (ZOE inhibit set reaction)
- care when acid etching; will remove thus etch around
Strong enough withstand amalgam condensation pressures
Thermal insulator (if >0.5mm thick)
Endodontics

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217
Q

Discuss composition of ZOE cements

A

Powder

  • ZnO (MgO)
  • Fillers: SiO2, Al2O3
  • dicalcium phosphate, rosin or micro (improve mixing)
  • zinc salt 1% (accelerate set)

Liquid

  • eugenol or oil of cloves
    (eugenol: substituted phenol, weakly acidic)
  • other oils: olive, cotton seed (modify viscosity)
  • acetic acid 1% (accelerate set)
  • H2O small amount (essential for set)
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218
Q

Discuss setting reaction of ZOE cements

A

Acid-base reaction
ZnO w/ eugenol forms zinc eugenolate (chelate complex)
H2O initiates reaction and is by-product
- will reverse in excess H2O

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219
Q

Discuss handling of ZOE cements

A

Mix glass slab/oil-resistant paper pad, incrementing powder
Mix 60-90s; work 2-3min; set <5min
Initial pH 5.5-6 up to 6-8 when set
High powder:liquid and smaller particle size = faster and stronger set

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220
Q

Discuss dis/advantages of of ZOE cements

A

Advantages

  • easy mix, handle
  • fast set in mouth
  • moisture accelerate set
  • good seal
  • non-irritant pH
  • obtundant when placed on dentine
  • thermal insulator
  • protect pulp from chemical irritant

Disadvantages

  • low compressive (15-25MPa) and tensile strengths
  • high H2O solubility
  • eugenol: potential allergen, mild irritant, inhibits vinyl polyermisation (can’t be used w/ composite/compomer)
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221
Q

Discuss reinforced ZOEs

A

10-40% synthetic resin is

  • added to powder
  • coated around powder particles
  • styrene or MMA added to liquid

Results

  • inc. compressive (40MPa) and tensile strength
  • red. H2O solubility
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222
Q

Uses of ZOE cements

A

When strength is not important but low irritancy is
Thermal insulating base
Temporary (few wks) and intermediate (1yr) restorations
Long-term cementation
Endodontics
Periodontal dressing
Not in direct contact w/ pulp

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223
Q

Compare Ca(OH)2 and ZOE cements

A

Moisture accelerates setting of both
ZOE stronger, less soluble and obtundent
Ca(OH)2 alkaline, antibacterial; stim. 2yr dentine
Eugenol in ZOE inhibit composite setting

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224
Q

Discuss ethoxy benzoic acid cements

A 
Composition 
Powder
- ZnO 60-75%
- fillers: SiO2, Al2O3 20-30%
- hydrogenated rosin 6%

Liquid

  • 50-65% eugenol in ZOE replaced by o-ethoxybenzoic acid
  • 30-35z eugenol

Properties

  • similar ZOE
  • better strength: compressive 60MPa
  • poor handling

Uses: similar ZOE, little in reality as other materials used

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225
Q

Discuss ZnO non-eugenol cements

A

Other oils will form cements w/ ZnO
Use w/ resin composites and materials formed by polymerisation
If pt allergic to eugenol

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226
Q

Discuss use of visible light cure resins as cavity liners

A

Similar to dental composites and light activator/initiator system

  • BisGMA or UDMA resins
  • phosphonated resins

Fillers

  • Ca(OH)2
  • F releasing glass
  • HA
  • calcium silicate

Advantages

  • tougher, less soluble
  • inc. resistance to etchants
  • alkaline surface pH but not antibacterial
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227
Q

Discuss calcium silicate based or MTA cements

A

Mainly used for endodontics
High strength
Alkaline pH
Bioactive; pulp repair

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228
Q

What are the preventative materials?

A 
Toothpaste, mouthwash
Topical F
- varnishes
- gels
- supplement tablets, solutions 
Sealants
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229
Q

Discuss F gels

A 
High viscosity H2O solution 
Flows around surface and sticks to teeth
Thixotropic (viscosity dec. w/ shear)
- technically plastic solution 
Professional application 3-6/12
Soluble polymer 
Low pH and neutral

F source 1-2%
- NaF, SnF2, acidulated phosphate fluoride

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230
Q

Discuss acidulated phosphate fluoride (APF) composition

A

pH 3

NaF 2%
HF 0.34%
Othrophosphoric acid 0.98%
Hydroxyalkyl cellulose (thickening)

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231
Q

Discuss fluoride varnish

A

5% NaF: 22600ppm F
1% difluorsilane: 1000ppm F

Natural resin and organic solvent
Thin film covers tooth surface 
CaF2 like deposit converts to fAP
6/12 application 
Bitter taste, transient tooth discolouration
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232
Q

Discuss pit and fissure sealants

A

For 1yr and permanent teeth
Red. caries
F release therapy
Clear, opaque or coloured

Ideal

  • high coefficient of penetration; flow into fissure
  • high surface tension
  • low viscosity
  • good wetting; stick and seal
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233
Q

Discuss resin sealants

A

BisGMA-based: diglycidil ether of bisphenol A w/ methacrylic acid
- MMA monomer or TEGDMA red. viscosity

UDMA-based: urethane dimethacrylates

LC: diketone-amine activation
Self/chemical cure: peroxide-amine activation

Limited DoC
O2 inhibition layer; unpolymerised monomer

Unfilled resin: good flow
Filled composite resin: SiO2/glass; improve wear resistance and radiopacity
Can incorporate F

Low viscosity, good penetration
Bond to protein matrix of enamel and dentine
Prone to hydrolysis
Low tensile strength and abrasion resistance

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234
Q

Discuss GIC sealants

A 
Low viscosity GIC
Excellent G release; high surface deposition 
Good adherence to enamel 
More viscous, lower penetration depth 
Lower retention, more brittle 
Less resistant to O wear
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235
Q

Discuss other sealants

A

RMGIC: better retention and wear cf GIC but lower cf resin based

Compomers: similar to resin-based

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236
Q

Define probing/pocket depth and attachment loss

A

Probing depth: distance (mm) from gingival margin to base of sulcus

Attachment loss: distance (mm) from cementoenamel junction to base of sulcus

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237
Q

Discuss the periodontal tissue

A

Supporting structures of teeth
Protect from masticatory forces, infection, facilitating normal function
Need to manage tissues to avoid periodontal problems, gum recession, dentine sensitivity, tooth mobility

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238
Q

Changes to gingiva in gingivitis

A

Colour change; v red
Change in consistency
Changes in contour; triangular papilla not sharp
Plaque and calculus in contact w/ inflamed tissue

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239
Q

Discuss the sulcus

A

In health 1-3mm deep
Gingival sulcus: space b/w free gingivae and tooth
Junctional epithelium forms base

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240
Q

Discuss junctional epithelium

A

Specialised epithelium, attaches to tooth surface, extends CEJ -> base gingival sulcus
Coronally 15-30 cells thick; Apically 1-3 cells
0.25-1.35mm length

2 basement membranes; internal and external basal lamina

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241
Q

Discuss function and adaptations of junctional epithelium

A

Located at interface b/w gingival sulcus (populated w/ bacteria) and periodontal soft and mineralised connective tissue need protection from bacteria

Structural and functional adaptations allow control constant microbiological challenge
Permeability allows GCF and defence cells to pass across to protect underlying tissues from disease

242
Q

Discuss periodontal ligament

A 
Connective tissue around and attach teeth to alveolar bone 
Fibres
- alveolar crest
- horizontal
- oblique
- apical fibres
- inter radicular
243
Q

What are Sharpey’s fibres?

A

Portion of principle PDL fibres embedded in cementum (tooth side) and alveolar bone (bone side)

244
Q

Discuss cementum

A

Thin layer bone-like tissue on roots for attachment of PDL
Possibly slowly deposited incrementally

Acellular: thin layer coronal 2/3 (10-30microm)
Cellular: thicker layer apical 1/3 (up to 120microm), contains cementocytes

245
Q

Define periodontal pocket

A

Gingival sulcus that has deepened due to loss periodontal attachment to >3mm depth

246
Q

Compare gingivitis and periodontitis

A

Gingivitis

  • characterised by tissue oedema, hyperaemia, neutrophil, crevicular fluid flow
  • severity associated w/ inc. lymphocytes and plasma cells in inflammatory infiltrate
  • reversible

Periodontitis

  • similar infiltrate to chronic gingivitis
  • alveolar crestal bone and PDL loss
  • pocket formation due to apical migration junctional epithelium
  • tooth mobility and loss
  • irreversible
247
Q

Discuss the epidemiology of periodontal disease

A 
Some almost universal adult popn. (>90%)
Strongly associated w/ levels of plaque
Severe pocketing infreq. (<10%)
Some members/subgroups more susceptible 
- physical, biological, behavioural, cultural, social factors
248
Q

Discuss the prevalence of gingivitis

A

Found in early childhood, inc. prevalence and severity in adolescence

> 1mm AL 99%
3mm AL in one site of mouth 53%
7mm AL 7%

249
Q

What are periodontal diseases?

A

Inflammatory reaction to accumulation plaque at gingival margin
Can lead to tooth loss
Divided into gingivitis and periodontitis

250
Q

4 main classifications of periodontal disease

A

Gingival diseases
Chronic periodontitis
Aggressive periodontitis
Periodontitis as manifestation of systemic disease

251
Q

Discuss gingival diseases

A

Dental plaque-induced gingival diseases

Non-plaque induced gingival lesions

252
Q

Discuss chronic periodontitis

A

Start as plaque-induced gingivitis
Loss of attachment and bone
- attachment loss equates w/ plaque levels
Host factors determine progression
Subgingival calculus invariably present
Localised <30% sites affected; generalised >30% sites
Mild, moderate, severe

253
Q

Discuss aggressive periodontitis

A

Group of severe, rapidly progressing forms
Common
- non-contributory medical history
- rapid attachment loss and bone destruction
- familiar tendency
Plaque levels inconsistent w/ severity of destruction

Localised: 1st molar/incisor, no more 2 teeth
Generalised
- <30yo
- generalised interproximal attachment loss
- episodic nature

254
Q

Risk factors of periodontal disease

A 
Anatomical: enamel pearls/root grooves/furcations/recession
Tooth position: malalignment/crowding/tipping
Iatrogenic: restorative margins/partial dentures/ortho
Systemic
Modifiable
- bacteria
-smoking 
- DM
- OH
- stress
- obesity
- immunodeficiency 
- medications 
- diet
- osteoporosis 
Non-modifiable 
- age
- genetics
- hormonal influences
255
Q

Predominant features of both gingivitis and periodontitis

A

Immune and inflammatory reactions to plaque bacteria

256
Q

Describe role of plaque in the progression of gingivitis

A

Inflammation develops immediately
Gram +ve bacteria accumulate supragingivally
After 24h changes evident, inc. blood flow
- bacterial mix more complex
- gram -ve colonise subgingivally

257
Q

5 stages of periodontal disease progression

A 
Health: pristine condition
Initial lesion: clinically healthy
Early lesion: early gingivitis
Established lesion: chronic gingivitis
Advanced lesion: chronic periodontitis
258
Q

Discuss the initial lesion stage of periodontal disease

A 
Acute inflammatory response
Clinical features 4-5d after accumulation of plaque
- reddening, swelling 
- tissue bleeding
- knife-edge papilla rolled, blunt
Inc. migration neutrophils into sulcus
Localised to gingival crevice
259
Q

Discuss early lesion stage periodontal disease

A

7-14d
Predominantly lymphocytes and neutrophils
Inc. vascularity
Collagen destruction; create space for inflammatory infiltrate

260
Q

Discuss established lesion of periodontal disease

A

Several wks
Plasma cells dominate and loss of collagen continues
Inflammatory infiltrate leukocytes and plasma cells
Bleeding gums
Subgingival plaque gram -ve
No PDL or alveolar bone loss

May remain stable w/o progression for months/yrs
- may become active and progress to advanced lesion

261
Q

Discuss advanced lesion of periodontal disease

A

Chronic local inflammation continues
Pockets develop where gingiva comes away from tooth
Collagen damage extensive
Junctional epithelium grows apically in response to destructive episodes
- attempt to maintain epithelial barrier creating periodontal pocket
Collagen breakdown of PDL fibres
Osteoclast stim.
Junctional epithelium continue apically; pocket deeper, harder to clean

262
Q

Discuss the host response to the biofilm

A

Biofilm produce substances which

  • directly injure host cell and tissue
  • activate inflammatory response
  • activate cellular or humoral immune response resulting in injury to PD tissues

Host response is essential to prevent serious infections
Can inadvertently cause local tissue damage and stim. attempts at tissue repair

263
Q

Discuss the host-microbial balance in periodontitis

A

Healthy gingiva consistently feature inflammatory cells
In response to continuous presence of bacteria in the crevice
Defence mechanisms stop progression to periodontitis

264
Q

Discuss the pathogenesis of periodontal disease

A

Plaque bacteria cause inflammatory response in soft tissues

PMNs, macrophages, lymphocytes migrate into tissue
PMNs phagocytose bacteria
PMNs accumulate in periodontal tissue
Inflammatory mediators released
Defence cells migrate into area
Tissues become red, swollen due to accumulation of fluid

265
Q

Discuss role of PMNs in inflammatory response

A

Predominant defence cell in crevice
Migrate from vessels into gingival tissues in response to stimuli (chemotaxis)
1st line

266
Q

Discuss cytokines role in inflammatory response

A

Proteins secreted by PMNs, macrophages that transmit signals
Inc. inflammation
Stim. bone resorption
Stim. collagen breakdown (fibroblasts)

267
Q

Discuss role of prostaglandins in inflammatory response

A

Produced by macrophages
Cause vasodilation
Stim. secretion inflammatory mediators
PGE2: stim. fibroblasts to produce MMP and osteoclasts

268
Q

Discuss role of MMPs in inflammatory response

A

Matrix metalloproteinases
Family enzymes that breakdown proteins
Collagenase

Produced by fibroblasts and PMNs
MMP levels inc. as tissue destruction occurs in periodontal disease

269
Q

Discuss bone resorption in periodontitis

A

Many of secreted factors involved in bone regulation and maintenance
Inc. osteoclast activity w/o inc. osteoblast = alveolar bone loss

Cytokines induce bone resorption by inc. expression RANKL while dec. OPG production in osteoblasts

  • RANKL on connective tissue, T-lymphocytes induce resorption
  • OPG inhibits RANKL
  • bacterial factors and host mediators induce RANKL expression
270
Q

Define fissure sealant

A

Material placed in pits/fissures in order to prevent/arrest development of caries; obliterates fissures and removes sheltered environment favourable for bacteria

271
Q

What are the pt and tooth indications for FS?

A

Pt: child w/

  • special needs
  • extensive caries in 1ry dentition
  • caries in permanent molars
Tooth: 6, E, 4/5, 2
- molars w/
— deep pits/fissures
— complex fissure patterns
— stained fissures
- incisors w/ deep cingulum pits
272
Q

Discuss the 3 materials used for FS

A

Unfilled resin

  • LC/chemical cure
  • clear, tinted, opaque

Filled resin

  • LC/chemical cure
  • clear, tinted, opaque
  • contain filler particles

GIC

  • useful when isolation is problematic
  • partially erupted teeth in high caries risk pt
273
Q

FS procedure

A

Clean tooth

  • prophylaxis doesn’t improve retention, advisable if plaque abundant
  • dry brush better than pumice/paste (can be retained)

Isolate: teamwork, cotton wool rolls, suction

Etch: 37% phosphoric acid 20s

Wash + dry: 10-15s w/ 3-in-1

Re-isolate

  • salivary contaminants allow precipitation of glycoproteins on enamel
  • greatly red. bond strength thus re-etch if necessary

Seal

  • apply to cover all pits/fissures/grooves up to 1/3 cuspal incline
  • LC 20s close as possible w/o touching
  • inspect for defects, remove excess w/ probe
  • check occlusion
  • follow up and review as per pt risk
274
Q

Discuss the cost effectiveness of FS and the 3 factors it depends on

A

Pits/fissure highly susceptible to caries, least likely to benefit from systemic or topical F-
FS prevent caries thus considered cost effective

Factors

  • caries in popn.
  • tooth to be sealed (molars more CE cf premolars)
  • retention/re-sealing necessary
275
Q

What is a preventative resin restoration?

A

Composite/GIC restoration w/ remaining pits/fissures sealed w/ FS

When stained fissure is caries lesion just into dentine in 1 area

276
Q

Describe the diagnosis technique for determining whether PRR req.

A

Thoroughly clean fissure of all debris, dry tooth, view in bright direct light

View good quality X-ray of tooth

If

  • micro-cavitation
  • shadowing visible under enamel adjacent to fissure
  • dentinal caries clearly visible on X-ray

Then conventional composite restoration limited to site of lesion and FS remaining fissure system

277
Q

Dis/advantage to PRR

A

Advantage
- appropriate management of early carious lesions may prevent pt entering restorative cycle unnecessarily

Disadvantage
- if FS approach adopted when managing suspicious fissure, careful long term monitoring and repair of FS is essential

278
Q

Materials for PRR

A

Unfilled resin
Filled resin
GIC

279
Q

PRR procedure

A

Remove soft plaque/organic substance w/ surface cleaning w/ or w/o pumice/oil-free prophypaste
LA, if caries just into dentine
Rubber dam if LA used OR dry guard, cotton wool rolls
Caries removal using small diameter but (tungsten carbide 330)

Etch: 37% phosphoric acid 15s
Wash + dry: 15s 3-in-1
Verify frosted appearance O surface

Apply prime to dentine 15s, air dry 5s
Apply bond to dentine 15s, air thin 3s
LC 20s
Apply composite resin to fill cavity
- if v small, flowable resin composite used
Apply FS cover fissures up to 1/3 cuspal incline
LC 20s, check occlusion and defects

280
Q

8 reasons for restoring 1ry teeth

A
  1. Eradicate disease; restore health, general wellbeing
  2. Give child simplest form of treatment: filling easier to accept cf pulpotomy/XLA
  3. Prevent pain and suffering: caries reaches pulp
  4. Avoid infection: caries exposure pulp, root canals, peri-radicular fissure
  5. Maintain arch length: space req. for eruption permanent teeth
  6. Restore function: mastication painful
  7. Psychological benefits
  8. Quality of life
281
Q

Compare 1ry and permanent molars

A

Thinner enamel
Comparatively greater thickness dentine over pulpal wall @ O fossa
Higher pulpal horns (esp. M), pulp chambers proportionately larger
Cervical ridges more pronounced esp. B aspect Ds
Enamel rods @ cervix slope occlusally rather than gingivally
1ry molars have markedly constricted neck
Roots longer, more slender cf crown size
Roots 1ry molars flare out nearer cervix

282
Q

Considerations in cavity preparation in 1ry dentition

A

Risk of pulpal exposure due to higher pulpal horns
B&L wall should be parallel outer surface
Isthmus width should be 1/3 intercuspal distance
No bevel @ gingival seat

283
Q

5 factors that impact on decision to restore 1ry dentition

A
  1. Developmental stage of child
  2. Caries risk assessment
  3. OH
  4. Parent compliance
  5. Child compliance
284
Q

6 materials used for restoring 1ry molar

A
  1. Amalgam
  2. Composite
  3. GIC
  4. RMGIC
  5. Compomer/PAMC
  6. Stainless steel crown
285
Q

Dis/advantages of amalgam 1ry molar restoration

A

+

  • ease of manipulation
  • durability
  • relatively low cost
  • red. technique sensitivity
  • not moisture sensitive

-

  • aesthetics
  • perceived safety
  • need mechanical retention = more tooth tissue removed
286
Q

Dis/advantages of composite 1ry molar restorations

A

+

  • aesthetics
  • minimal tooth removal

-

  • polymerisation shrinkage
  • technique sensitive
  • good isolation/pt compliance
  • time consuming
  • not suitable large, multiple surface restorations
287
Q

Dis/advantages GIC and advantage RMGIC

A

+

  • chemical bonding
  • thermal expansion similar
  • biocompatible
  • uptake/release F-
  • dec. moisture sensitivity
  • wear resistance and aesthetics cf composite

RMGIC +
- better wear resistance cf GIC

288
Q

Dis/advantages SSC

A

+

  • durable
  • inexpensive
  • minimal sensitivity
  • full coronal coverage
  • aesthetics
289
Q

Outline principles involved in preparation of O cavity in 1ry molar

A

External outline

  • gain access w/ 330 deepest pit first
  • extend to remove all caries incl. susceptible pits/fissures
  • smooth outline
  • contour outline parallel to M&D ridges
  • width less than 1/3 O table

Internal outline

  • 0.5mm into dentine (1.5mm total depth min. acceptable depth amalgam 1ry)
  • rounded pulpal line angles
  • cavo-surface 90 degrees
  • lat. wall undercuts
290
Q

Outline procedure for proximal 1ry amalgam restoration

A

O outline as Class 1mw/ 330
Extend O outline to marginal ridge

@ marginal ridge, use but in buccal-lingual pendulum
- going down in gingival direction to break contact point
Isthmus @ widest point >1/3 width O table

Proximal extension to cleansable region and @ 90 degree to axial surface tooth

Proximal box widest @ gingival margin

  • 1mm deep, perp. axial wall
  • width from surface to axial wall 1mm
  • B and L walls diverge towards gingival margin
  • floor flat or slightly concave gingivally

Axial wall follows contour missing tooth surface
Gingival floor clear of contact area and not sub-gingival

291
Q

Indications for SSC

A

2/+ carious surfaces or extensive 1 surface caries
Following pulp therapy 1ry molar
Developmental problems; hypoplasia, AI, DI
# 1ry molar
Excess tissue loss; attrition, abrasion, erosion
High caries risk pt
As abutment for certain appliances, space maintainers
Special needs pt w/ red. OH and/or breakdown intra-coronal restoration likely
GA pt undergoing restorative care if 2/+ surfaces involved
Pt w/ infra-occluded 1ry molars to maintain mesio-distal space

292
Q

Contraindications for SSC

A

1ry molar close to exfoliation w/ more than 1/2 root resorbed
Pt w/ known nickel allergy or sensitivity

293
Q

Discuss SSC procedure

A

LA, RB preferable
Caries removal, appropriate pulp treatment if req.

Place M and D wedges (gingival to contact area)
- protect tissues and red. contamination
M and D surfaces removed using fine tapered fissure bur/diamond
- cut through contact point w/o damaging adjacent tooth
- angle bur away from vertical so should not created at gingival margin

Same bur/330 used to red. O surface to allow 1-1.5mm space b/w tooth and opposing dentition

Try on crown, check sitting in gingival crevice

  • crimp if sits on gingival crevice, re-try
  • if over extended, cut back using scissors/stone, smooth edges w/ stone/rubber wheel

Wash and dry, cement w/ GIC
- seat crown L to B, pressing firmly
Remove excess w/ probe, floss, gauze
Check occlusion, 1mm accommodation if high

294
Q

What is the Hall technique?

A

Method for managing carious 1ry molars w/o LA, tooth preparation or caries removal

295
Q

Outline the Hall technique procedure

A 
Assess tooth shape, contact points
Sit child slightly upright
Protect airway
Size crown
Cement crown
Fit crown
296
Q

Macroscopic structural properties of enamel

A

Greyish/blueish-white; appears yellowish-white as semi-translucent and reflect underlying colour of dentine
Thickness: 0-2mm(I) 2.6mm (M)
Selectively permeable
Refractive index: 1.655 (porcelain 1.5 Quartz 1.54)
Acid soluble

297
Q

Microscopic properties of enamel

A

Needle-like crystals: 50nm x 25nm, several mm long
Cluster into enamel prisms containing ~1000 crystallites
Prisms arranged into larger arrays w/ interprismatic enamel

298
Q

What method is used to study crystallite alignment and direction?

A

Synchrotron X-ray diffraction

299
Q

General macroscopic mechanical properties of enamel

A

Hardness: Moh scale 5-8
Compressive: 350 MPa
Shear: 90 MPa
Tensile: 10 MPa

300
Q

Discuss elastic modulus and hardness of enamel

A

Varies 50 - >100 GPa
Macro scale test show lower elastic modulus than micro/nano-scale
Cross-sectional enamel has lower elastic modulus cf surface enamel
Higher load applied, lower elastic modulus

301
Q

Discuss # toughness of enamel

A

Crack propagation and subsequent # leads to ultimate structural failure
Quantitative way of expressing material’s resistance to brittle # when crack present
High # toughness show improved clinical performance and reliability

302
Q

Discuss structure-function relationship of enamel w/ regards to enamel microstructures

A

Nano-scale HAP crystallites have higher strength than bulk materials
Critical crystallite thickness ~30nm; enamel optimised for stress resistance
Balance b/w wear and fracture resistance
- wear: oriented rods red. wear by inc. hardness
- #: inter-rod structure holt cracks

303
Q

Discuss structure-function relationship of enamel w/ regards to protein remnants

A

Under load protein macromolecule chains may deform; polymer-like behaviour
Thermodynamically unstable therefore will return to initial form and position upon release of load (elastic behaviour)

304
Q

Compare #/failure of restored vs unrestored tooth

A

Fracture resistance of unrestored always > restored regardless of cavity shape and material
High stress at tooth-restoration interface can cause crack propagation and fatigue failure on mastication

305
Q

Factors have to be considered to decide optimal cavity shape

A

Min. reduction of tooth tissue to preserve max. tooth
Material used
Geometry of cavity
Keep stress level low to avoid # of restoration

306
Q

Factors impacting on geometry of cavity

A

Size and type of tooth
Type of cavity: non/undercut
Material: amalgam, composite, GIC, porcelains, gold

307
Q

Discuss where stress is and where cracks propagate in bonded and non-bonded materials

A

Bonded

  • stress @ cuspal edge/restoration edge
  • cracks occur within enamel in contact w/ opposing tooth

Non-bonded

  • stress throughout material interface b/w restoration and tissue, corners cavity
  • cracks occur in internal line angles and EDJ
308
Q

Define macroscopic and microscopic cavity modifications

A

Macro: large scale modification, using burs
Micro: small scale, chemically

309
Q

Define cavosurface angle and line angle

A

Cavosurface: angle b/w cavity wall and surface of tooth

Line angle: angle b/w any 2 surfaces of tooth; mesiolingual

310
Q

Discuss macro and microscopic preparations for amalgam cavity

A

Macro

  • enamel undercuts; bottom wider than top, retention
  • slots and grooves; resistance and retention, pack amalgam into
  • cavosurface angle; 90, follows lines of prisms
  • flat surface; resistance

Micro

  • no inherent bonding
  • bonded amalgam
311
Q

Macroscopic features of composite/GIC cavities

A

Enamel margin bevel

  • remove grossly unsupported enamel
  • inc. SA bonding
  • better marginal seal

+ same as amalgam

312
Q

Microscopic features of composite cavity

A

Etch + prime/bond

  • remove smear layer dentine
  • selectively demineralises enamel prisms
  • create micromechanical undercuts for resin to engage

Hybrid layer

  • demineralised resin-impregnated dentine
  • etch remove smear layer
  • demineralised intertubular dentine, expose collagen
  • resin flow into, form tags
313
Q

Microscopic GIC cavity preparations

A

Conditions

  • 10% polyacrylic/citric acid
  • remove smear layer
  • prepare surface for Ca2+ bonding
314
Q

Define screening

A

Simple test performed on large number of people to identify those most likely to develop specific disease

315
Q

Why are PD assessments performed?

A

GDC

  • competent at completing a PD exam and charting, diagnosis and treatment plan
  • provide good standard of care and 1ry disease control for pt
316
Q

How is PD health assessed?

A 
Gingival colour, contour, recession
Pocket depth
Bleeding on probing
Tooth mobility
Furcation involvement
X-rays
317
Q

Describe healthy PD tissue

A 
Pink
Stippled; firmly adherent to underlying bone
No bleeding
Little recession 
No mobility 
Pocket depth <3mm
318
Q

What problems are found when measuring PD disease?

A

Full assessment (plaque, calculus, bleeding, pocketing) v T consuming
Use index to get quick, rough measurement; plaque index
Use screening method to identify those who need complete assessment (BPE)

319
Q

Define false pocket and true pocket

A

False: inc. probing due to gingival swelling/overgrowth, no attachment loss

True: inc. probing due to loss of PD attachment

320
Q

Describe the BPE procedure

A

Used as part of all routine dental exams; adults, child 7+
Intended to identify those w/ established periodontitis

Dentition divided into sextants; 7-4, 3-3, 4-7
- only highest score recorded for each

Carried out w/ WHO probe

  • gently inserted inti gingival crevice, walked around
  • side kept in contact w/ and parallel w/ root surface
321
Q

How does PBE take place for children?

A

Check 6 teeth

  • UR6 UR1 UL6
  • LR6 LL1 LL6

If 7-12; use codes 0-2
12+ all codes
Only if compliant

322
Q

Dis/advantages of BPE

A

Advantages

  • simple, rapid
  • good indication of appropriate treatment

Disadvantages

  • not designed to monitor pt (misused)
  • no distinction b/w true/false pockets
  • lack detail in sextant
  • lack detail about recession
  • lack detail about furcation involvement
323
Q

Discuss the 6 point pocket chart (6PPC)

A 
Used when req. full PD assessment 
6 measurements for each tooth
Same walking technique as PBE
Use Williams or UNC15 probe 
Note bleeding on probing
324
Q

Common probing errors for PBE

A 
Interference from calculus on tooth/root
Presence of overhanging restoration 
Incorrect angulation of probe 
Amount of pressure applied to probe 
Misreading probe
325
Q

PBE codes 0-4

A

0

  • <3.5mm, black band visible
  • no bleeding or calculus
  • no treatment

1

  • <3.5mm, black band visible
  • bleeding on probing, no calculus
  • OHI

2

  • <3.5mm, black band visible
  • possible bleeding, calculus
  • OHI, SP, eliminate plaque retentive restorative margins

3

  • 3.5-5.5mm, black band partially visible
  • possible bleeding, calculus
  • OHI, SP, root surface debridement, eliminate plaque retentive restorative margins

4

  • > 5.5mm, black band not visible
  • possible bleeding, calculus
  • complex treatment in addition to 3
326
Q

PDE codes X and *

A

X: edentulous or 1 functioning tooth

*: furcation involvement

327
Q

Discuss alveolar bone

A

External plate cortical bone
Inner socket thin compact bone seen as lamina dura on X-ray
Cancellous trabeculae b/w external plates supporting alveolar bone

328
Q

Discuss bone loss in relation to radiographic PD assessment

A

Bony crest usually 1-2mm apical to CEJ
Clinical crown:root: amount root remaining in bone compared to amount of tooth above bone level

Horizontal bone loss

  • level of bone essentially equal interdentally (b/w 2 teeth)
  • measured as % bone lost

Vertical bone loss

  • 1 tooth has more bone loss than adjacent tooth
  • bone crest more apical to CEJ in 1 tooth cf adjacent tooth
329
Q

What are X-rays used to visualise in PD assessment?

A

Bone levels
Root length and shape
Furcation
Restorative status; filling, caries, RCT

330
Q

Discuss different types of X-ray in relation to PD assessment

A

Horizontal BW
- show crestal bone, caries; pocket depth <5mm

Vertical BW
- film turned 90; moderate-severe periodontitis; bone level several teeth

PA
- severe periodontitis; tooth morphology, furcation, root shape, periodontal-endodontic status

PAN
- all teeth on 1 film

331
Q

Define amalgam and dental amalgam

A

Amalgam: when Hg mixed w/ another metal

Dental: Hg + Ag-Sn alloy

332
Q

Compare composition low Cu and high Cu dental amalgams

A 
Low Cu/conventional/traditional 
Ag 67-74%
Sn 25-28%
Cu 0-6%
Zn 0-2%
\+ Hg
High Cu
Ag 40-70%
Sn 21-30%
Cu 12-30%
Zn 0-1%
Pd 0-0.5%
In 0-4%
333
Q

Function of Ag and Sn in amalgam

A

Ag
Inc: strength, tarnish and corrosion resistance, expansion
Dec: flow and creep, setting time

Sn
Inc: flow and creep, setting time
Dec: strength, expansion, corrosion resistance

334
Q

Function of Cu and In in amalgam

A

Cu
Inc: strength and hardness, tarnish and corrosion resistance, expansion
Dec: flow and creep, setting time

In
Inc: strength, expansion, setting time
Dec: flow and creep, surface tension thus less amount Hg req.

335
Q

Function of Zn, Hg, Pd in amalgam

A

Zn: scavenger, dec. oxidation other metals

Hg: activates reaction

Pd: inc: tarnish and corrosion resistance, strength

336
Q

Different composition combinations possible of amalgams

A

2 different alloys (admix/dispersed phase): Ag3Sn + AgCu
- dispersaloy, Caulk 69% Ag + 18%Sn + 12%Cu +1%Zn; Ag3Sn + AgCuOd

Single ternary alloy (unicompositional): AgSnCu
- Tytin, Kerr 59%Ag + 13%Sn + 28%Cu

Quaternary alloy: AgSnCuIn

337
Q

2 possible particle shape combinations of amalgam

A

Lathe cut

Spherical

338
Q

Discuss lathe cut amalgam particles

A

Alloy ingot: mixture gamma and beta phases
Homogenising: form gamma phase; 400 degrees 8h
Particles cut from ingot

Aged: parties annealed @ 100 degrees, relieve internal strains
Surface treated w/ acid; inc. reactivity

L: 60-100microm; W: 10-70microm; T: 10-35microm
Micro-/fine-/coarse-cut

339
Q

Discuss spherical amalgam particles

A

Produced by atomising molten alloy in inert atmosphere
Acid wash to inc. reactivity
5-50microm size

340
Q

Compare lathe-cut and spherical particles

A 
Spherical particles:
Req. less Hg 40-45%
Less mixing T
Lower condensation pressures
Harden more rapidly 
Smooth surface
341
Q

How can amalgams be classified?

A

Cu content: high and low Cu alloys
Zn content: Zn free and containing
Alloy: binary, ternary, quaternary
Shape: lathe-cut, spherical, admix

342
Q

Discuss trituration if amalgam

A

Carried out in mechanical mixer
3000rpm 5-20s
Powder mixed w/ 40-50% Hg
- higher amount low Cu alloy

343
Q

Discuss how to tell correct trituration has occurred

A

Under: dull, dry, crumbly

Properly: shiny, smooth, separates from capsule in single mix

Over: shiny, hot, wet, sticks to capsule

344
Q

Discuss condensation of amalgam

A 
Packed incrementally into cavity 
Condensed to:
- remove excess Hg
- prevent voids
- give optimal marginal adaptation

Final Hg content

  • 45% lathe-cut
  • 40% spherical
345
Q

Difference b/w packing of lathe-cut and spherical amalgams

A

Lathe: small condenser tip w/ high pressure
Spherical: large condenser tip w/ low pressure

346
Q

Discuss setting of amalgam

A

Hg initially dissolves surface of alloy particles
New Hg containing alloys formed
Need to condense prior to crystallisation of new alloy
Reaction never complete
Set amalgam contains unreacted Ag3Sn in matrix of new alloys
- cored structure

347
Q

Discuss the phases of conventional/low Cu alloys

A

Hg dissolves Ag and Sn from alloy; new intermetallic compounds form

Gamma: Ag3Sn

  • unreacted alloy
  • strongest, corrodes 2nd least
  • 30% vol set amalgam

Gamma 1: Ag2Hg3

  • matrix for unreacted alloy particles
  • 2nd strongest, corrodes least
  • 60% vol

Gamma 2: Sn7-8Hg

  • weakest, softest
  • corrodes fast, voids form
  • 10% vol: dec. w/ T due to corrosion
348
Q

Discuss admired high Cu alloys

A

Hg dissolves

  • Ag from AgCu spherical eutectic particles
  • Ag and Sn from Ag3Sn

Reaction

  • AgCu remains unreacted
  • gamma 2 react w/ AgCu to form Cu6Sn5 (eta phase)
  • around unconsumed Ag-Cu particles
349
Q

Discuss single phase high Cu alloy

A

Gamma (Ag3Sn) w/ epsilon (Cu3Sn) coating
Ag and Sn dissolve in Hg
Gamma 1 (Ag2Hg3) crystals grown binding together gamma particles
Eta (Cu6Sn5) crystals growth within gamma 1

350
Q

Discuss the finishing of amalgam restoration

A

Carving

  • function size and shape alloy
  • spherical better surface finish

Burnishing

  • removal residual Hg
  • better margins

Polishing

  • necessary(?)
  • aesthetics
351
Q

Discuss dimensional changes of amalgam during setting

A

All amalgams have net shrinkage

Initial shrinkage from dissolution of alloy (~20mins)
Expansion from growth of new crystalline phases
- higher Hg content, higher expansion

Stable after 6-8h

352
Q

Factors that inc. shrinkage of amalgam

A

Smaller particle size: inc. dissolution
Higher Hg:alloy ratio: inc. dissolution
Trituration T longer, more rapid: inc. dissolution
Inc. condensation pressure: lower Hg, less new alloy formed

353
Q

Discuss dimensional changes of amalgam restoration after setting

A

Delayed expansion

Zn containing alloy contaminated w/ H2O, H2 gas evolved causing expansion and possible pain if pressure on pulp

354
Q

Discuss tarnish of amalgam

A

Surface discolouration
Formation black silver sulphide
- can be polished off

No long term problems or effect on clinical lifetime

355
Q

Which phase in low and high Cu alloys most prone to corrosion?

A

Low Cu: gamma 2 (Sn7-8Hg) phase
- products: tin oxides and chlorides

High Cu: eta (Cu6Sn5) phase
- products: tin oxides and chlorides, CuCl

356
Q

Discuss different types of corrosion in amalgam

A

Galvanic: opposing dissimilar metals
- amalgam w/ gold casting alloy

Localised galvanic: different phases within same alloy
- Ag-Hg and Ag Sn Cu

Crevice: plaque build-up causes differences in surface O2 levels, inc. electronegativity cf clean surface forming anode

Stress: under sustained tensile force in corrosive environment, cause crack

357
Q

Discuss mechanical properties of amalgam

A

High compressive strength
Tensile 50-60MPa
Good wear resistance
Hg content critical to strength

358
Q

Compare mechanical properties of low and high Cu alloys

A

Low Cu lathe

  • 2.5% creep
  • 94MPa CS 1h
  • 410MPa CS 24h

High Cu admix

  • 0.25% creep
  • 226MPa CS 1h
  • 440MPa CS 24h

High Cu spherical

  • 0.05% creep
  • 315MPa CS 1h
  • 500MPa CS 24h
359
Q

Discuss disadvantages of amalgam

A 
Non-adhesive; mechanical retention 
Conductive
- heat: high thermal conductivity and diffusivity 
- electricity: galvanic effects 
Corrosion and tarnish
Poor aesthetics 
Brittle and weak in thin section
Viscoelastic; creep
360
Q

Discuss factors affecting marginal seal of amalgam restorations

A

Coefficient thermal expansion: > dentine = marginal leakage

Low Cu corrode = sealing of margins, slower for high Cu

Metal sulphides (tarnish) form @ margins, give seal w/ T

Varnishes
Creep

361
Q

Discuss use of varnishes for marginal seal of amalgam

A

Cavity varnish: resin in volatile solvent

Seal dentine surface; red. bacterial inflammation
Coat surface and margins w/ unfilled resin; delay microleakage until corrosion products seal
Bonding agents available

362
Q

Discuss how creep can affect marginal seal of amalgams

A

Can lead to flow over margins
Amalgam brittle and weak in thin section thus #s
Margin deterioration or ditching

Over filling can have similar effect

363
Q

Discuss factors affecting quality of amalgam restoration controlled by manufacturer and dentist

A

Manufacturer

  • alloy composition
  • heat treatment of alloy
  • size, shape, method of production of alloy particles
  • surface treatment of particles
  • supplied form
  • Hg:alloy ratio

Dentist

  • trituration procedure
  • cavity design
  • condensation technique
  • marginal integrity
  • anatomy
  • final finish
364
Q

Discuss different forms Hg

A

Elemental: absorbed through lungs

Inorganic Hg-S: as found in nature, lungs

Organic Hg-(CH3)2

  • highest toxicity
  • used as fungicide/herbicide
  • absorbed GIT
365
Q

Discuss the toxicity of Hg

A

Actively secreted, t1/2 ~55d

Low level toxicity recoverable
Greatest danger from Hg vapour, high vapour pressure
Other routes: skin contact, airborne droplets

Wear and corrosion release Hg (< WHO threshold)
Released Hg reacts w/ unreacted Ag-Sn alloy

Rare cases allergy

366
Q

Discuss amalgam tattoos

A

Accidental implantation Ag containing compounds into oral mucosal tissue
Greyish black pigmentation

Occurs

  • removal old amalgam
  • particles entering surgical wound
  • amalgam dust in oral fluids

Seen: gingiva, buccal mucosa, alveolar mucosa

367
Q

Factors affecting choice of DM in paediatrics

A 
Clinical situation, National guidelines 
Tooth structure, cavity depth
Longevity
Toxicity
Pt compliance
- procedure length
- moisture control 
Parents consent
368
Q

Dis/advantages of amalgam

A

Advantages

  • good longevity
  • cost effective, economical, easy to use
  • excellent mechanical properties
  • v low shrinkage
  • not moisture sensitive

Disadvantages

  • poor aesthetics
  • retentive cavity req.
  • 2mm min depth
  • safety
369
Q

Dis/advantages of composite

A

Advantages

  • good creep resistance, compressive strength
  • mechanical properties

Disadvantages
- not natively adhesive; acid-etch: micromechanical retention
— good adhesive bond but difficult to achieve
- polymerisation shrinkage
- dentine bonding weaker cf acid-etch enamel
- poor wear resistance; high wear contact areas
- thermal expansion mismatch
- not complete polymerisation
— potential leaching of toxic monomer (BPA)

370
Q

Dis/advantages of GICs

A

Advantages

  • chemical bond
  • -COOH binds Ca2+ in HAP
  • F- release/uptake
  • no shrinkage or exotherm
  • not toxic
  • ease of placement in bulk
  • ultra conservative
  • aesthetic

Disadvantages

  • low strength, high wear @ early stage
  • need protection from dehydration
  • low diametral/tensile strength
  • need support by tooth structure
371
Q

Dis/advantages RMGIC

A 
Cf GIC
advantage 
- command set (LC; FR polymerisation of methacrylate group of HEMA polymer)
- tougher
- early strength 
- improved longevity

Disadvantages

  • can set in dark
  • HEMA cytotoxic
372
Q

Dis/advantages of PAMC/compomers

A

Advantages

  • F release delayed
  • longevity
  • coloured restorations (paediatrics)
  • greater strength cf GIC, RMGIC

Disadvantage

  • shrinkage
  • exothermic
  • bonding req.
373
Q

Discuss stainless steel in preformed metal crowns/SSCs

A

Chromium-nickel steel of surgical grade
Alloy: Fe-C

Resistant to corrosion due to Cr: Cr2O3 forms @ surface

Ferritic, austenitic (most stable), martensitic

Highest corrosion resistance
Malleable

374
Q

Discuss dis/advantages SSCs

A

Advantages

  • strong; tensile 600MPa
  • durable
  • preventative
  • cost effective long term
  • prefabricated sizes
  • cemented w/ GIC, zinc phosphate/polycarboxylate
Disadvantages 
- complex procedure 
- Ni/Cr allergy/sensitivity 
- aesthetics 
— veneer crown; resin composite 
— tooth colour prefabricated
375
Q

List dental materials in order of inc. pH

A 
Phosphoric acid solution 1.5
PAA 2.5
Zn phosphate 3.0
GIC 3.5
Zn polycarboxylate 4.0
ZOE 5.0
CaOH2 9.0
376
Q

List dental materials in order of dec. pulpal irritation

A

Zn phosphate
GIC
Zn polycarboxylate
ZOE, CaOH2

377
Q

List dental materials in order of inc. solubility

A 
Composite
GIC, Zn phosphate
Zn polycarboxylate 
ZOE
CaOH2
378
Q

Define thermal conductivity and thermal diffusivity

A

Conductivity: quantity heat/s passing through 1cm3 w/ temp inc. 1 degree
- how easily heat transfers through material

Diffusivity: rate of transfer of heat from hot side to cold side
- time for 2 ends to be @ same temp

379
Q

List dental materials in dec. thermal conductivity, diffusivity and expansion

A

Conductivity
Amalgam»composite=Zn phosphate>GIC>ZOE=dentine

Diffusivity
Amalgam»composite>ZOE>Zn phosphate>GIC=dentine

Expansion
Composite>ZOE>amalgam>GIC=tooth

380
Q

What is gypsum?

A

Calcium sulphate dihydrate (CaSO4)2H2O

Mineral found in nature

381
Q

General uses of gypsum products

A

Impression materials
- -ve replica OC, limited use today (edentulous)

Models

  • study cast (+ve replica OC) replica of fitting surfaces OC
  • poured from impression to construct partial/full denture

Dies
- +ve replica individual tooth

Moulds
- for construction denture

Refractory investment

382
Q

What do manufacturers convert (CaSO4)2H2O into? What does this form?

A

Hemihydrate: (CaSO4)H2O

Plaster

  • soft, white powder
  • large, irregular, porous particles
  • not closely packed when set

Stone (Hydrocal)

  • harder, yellow powder
  • small, regular, non-porous parties

Improved stone (Densite, Fuji Rock)

  • expensive
  • improved scratch resistance cf stone
383
Q

What are alpha and beta hemihydrates? Compare structure

A

Alpha: improved/stone
Beta: plaster

Differ in particle/crystal size and SA

Beta: weak product; large, irregular, porous particles don’t pack closely = large pores in set material

Alpha: strong product; small, regular, non-porous particles pack closely in set

384
Q

Uses of plaster

A

Softer, cheap, easy to use and shape

General purpose material for mounting models into articulators
Flasking procedures for complete/partial denture processing
Rudimentary functions; basing models (ortho study casts)

385
Q

Uses of improved/stone

A

Dies

  • models of mouth
  • replica individual teeth
  • construction crown and bridges

Where max. strength essential for dentate casts
Study casts

386
Q

Composition of gypsum products

A

All chemically identical

Hemihydrate (alpha and beta) 75-85%
Unchanged gypsum (dihydrate) 5-8%
Mix: fast set soluble (hexagonal CaSO4) and slow set insoluble (orthorhombic CaSO4) anhydrites 
Impurities ~4%
Accelerators/retarder ~4%
387
Q

How do accelerators/retarders affect setting T?

A

Inc./dec. solubility of gypsum

388
Q

Discuss gypsum accelerators

A

Speed up setting T

K2SO4 reacts w/ H2O/hemihydrate -> syngenite [K2(CaSO4)2H2O]

  • crystallises rapidly
  • promote crystal growth
  • red. overall expansion

(CaSO4)2H2O

  • additional nucleation sites
  • red. working, setting T

NaCl <20%

  • additional crystallisation sites
  • inc. reaction rate
  • red. observed expansion
389
Q

Discuss retarders

A

All interfere w/ crystal formation and affect dimensional change on setting

NaCl >20%

  • slows down setting
  • dec. reaction rate; deposit on crystals preventing growth

Borax: counteract inc. reaction rate

Potassium citrate: gum arabic, acetates

390
Q

Discuss chemistry of setting of gypsum products

A

(CaSO4)2H2O + H2O -> 2(CaSO42H2O) (exothermic)

Addition of water forms wet slurry which subsequently hardens

Water content
- theoretically 8.6ml req. 100ml hemihydrate -> dihydrate
— for smooth, workable mix more req.
- 100g plaster/stone/improved stone 50/20/20ml H2O
- plaster: large, irregular particles form porosity H2O must fill to form mix

391
Q

Discuss setting mechanism of gypsum products

A

Hemihydrate slowly forms dihydrate

Some hemihydrate dissolves in H2O and reacts forming dihydrate
Lower solubility of dihydrate results in unstable, supersaturated solution
(CaSO4)2(H2O) precipitates forming stable crystals

More hemihydrate dissolves, continues until set

Unchanged gypsum dihydrate acts as crystallisation nuclei for growing dihydrate crystals
Setting begins when growing monoclinic crystals interlock -> expansion plaster/stone

392
Q

Discuss factors affecting setting of gypsum products

A

Inc. P/L ratio

  • H2O: slower set (longer for saturation); mix runny, model weaker
  • powder: difficult mix, porosity within set material

Inc. spatulation T (how long mix)

  • red. setting T
  • break formed crystals, form new sites crystal growth
  • inc. setting expansion

Inc. spatulation rate (how fast mix)
- red. setting T, inc. expansion

Inc. temp.
- minimal effect; v hot could accelerate set

393
Q

Discuss the setting expansion of gypsum products

A

Crystals impinge on one another as grow, push each other apart leading to expansion
Large empty spaces form b/w resulting in porosity, leading to expansion (0.6% by vol)
- plaster 0.2-0.4%; stone 0.08-0.1%; improved 0.05-0.07%)

Importance

  • dies, moulds slightly larger than oral anatomy
  • crowns, bridges, dentures not too tight fit

Hygroscopic expansion

  • crystals grow freely in water
  • immerse material in H2O while setting inc. expansion
394
Q

Discuss properties gypsum products

A 
Little/no dimensional changes once set 
Excellent storage 
Dry strength 2x wet strength 
Tensile
- plaster 20MPa; v low; teeth margins can break 
- stone; 2x plaster; crown, bridge models, dies
Hardness
- plaster v low
- better for stone, improved stone best
Abrasion resistance 
- plaster highly susceptible 
- stone/improved; better resistance
395
Q

Case for prevention of decay in children

A

Tooth decay most common dental disease affecting children
Poor OH impact on general health, wellbeing, growth, development
Largely preventable
Huge burden on NHS

396
Q

Discuss caries risk assessment in children as preventative risk strategy

A

Caries risk assessment

  • think about disease
  • lost etiological factors in order of importance (presence of caries most important)
  • identify risk category
397
Q

Describe the 3 risk categories of caries in children

A

Low

  • no caries, favourable family history, good diet, good OH, well motivated
  • access to fluoride/fluoridated water

Moderate: new lesions per 2 year

High

  • lesions per year
  • ortho
  • chronic illness / physically/medically compromised
  • social risk factors
398
Q

Outline the 3 principles of prevention of dental caries in children

A

1ry: stop disease from starting or keeping teeth healthy before disease occurs
2ry: detect disease and prevent further development or limit impact of disease @ early stage
3ry: treat disease, restore function, prevent further development or rehabilitation of decayed teeth w/ further preventive care

399
Q

Outline 1ry preventative methodologies for children

A 
Brush 2x daily
Brush last thing @ night, 1 other time
Use fluoridated toothpaste
Spit don’t rinse
Freq. and amount sugar red./limited to meals; not more 4x/d
400
Q

Outline 2ry preventative methodologies for children

A 
BWs
Occlusal caries
- clinically into dentine; repair 
- fissure system only; PRR
Approximal/smooth surface
- enamel only; fluoride, dec. sugar, inc. brushing
401
Q

Outline 3ry preventative methodologies for children

A 
Restoring decayed tooth
- restore function 
- prevent further disease progression 
XLA if prognosis poor
- prevent further disease progression
- rehabilitation decayed teeth
402
Q

Outline steps in treatment planning for prevention in children

A 
Pain relief 
Prevention 
- OH
- appropriate fluoride
- dietary control
- FS
- appropriate X-ray 
Desiree dentition
403
Q

Discuss OH regimen in prevention of caries in children

A 
Advise and encourage effective OH regime
Advise/demonstrate brushing methods 
Emphasis of systematic brushing 
Supervised brushing <7
Spit not rinse
404
Q

Discuss appropriate fluoride in prevention of caries in children

A

Depends on age/risk
Professional topical application @ intervals depending on risk
Daily use of fluoridate toothpaste
Mouth rinse >8 (risk dependent)
High F toothpastes 2800/5000ppm (risk dependent)

405
Q

Discuss diet control and FS in prevention of caries in children

A

Diet

  • keep diet diary
  • 4d/24h
  • food, drink, snacks
  • advice on sugar freq./intake, substitutes

FS; usually permanent molar, depends on risk

406
Q

5 criteria for failed restoration

A

2ry/recurrent disease

  • invasive caries in dentine
  • pulpal necrosis

Loss of function

  • lost restoration
  • loss surrounding tissue

Inevitable progression to caries

Microleakage causing sensitivity or pain

Appear unacceptable to pt

407
Q

Discuss invasive caries into dentine as reason for failed restoration

A

Symptoms

  • usually none
  • discolouration ant.
  • pulpitis

Signs marginally

  • visual; not approximally
  • radiography; approximally
  • tactile

Signs deep tissue

  • visual; sometimes
  • radiography; sometimes
408
Q

Discuss pulpal necrosis as reason for restoration failure

A

Symptoms; pulpitis

Signs

  • loss of vitality on sensibility testing
  • +/- peri-radicular radiographic change
409
Q

Discuss loss of function and progression to caries as reasons for restoration failure

A

Loss of function; lost restoration/surrounding tissue

  • restoration loose or lost
  • # tooth/cusp causing loss occluding surface; discomfort

Progression to caries

  • # restoration -> microleakage
  • loss of marginal integrity -> microleakage
  • microleakage = bacteria ingress and caries -> sensitivity or pain
410
Q

Discuss unacceptable appearance as reason for restoration failure

A 
Marginal staining (ant.)
Discolouration of ant. material 
Contrast w/ normal darkening of tooth
Gingival recession; darker roots
Desire for white fillings
411
Q

4 main reasons for failed restorations

A

Pt factors
Operator factors
Material factors
Chance (trauma)

412
Q

Discuss pt factors for failed restorations

A 
Cariogenic factors unchanged
- diet
- plaque
- saliva/xerostomia
- poor OH
Para-functional habits
Appearance unacceptable
413
Q

2 main areas where operator errors can cause failure of restoration

A

Errors in planning

Errors in execution

414
Q

Discuss errors in planning for failure of restoration

A

Failure to

  • promote prevention
  • check occlusion before tooth management
  • take account whole pt; management of caries and periodontitis risk

Inappropriate

  • restoration for tooth or situation
  • restorative material; incl. lining and base
415
Q

Discuss errors in execution causing failure of restorations

A

Damage to pulp-dentine complex

  • over-cutting/pulp exposure
  • excessive heat or pressure

Leaving infected carious tissue
Unsatisfactory cavity design for material

Failure to

  • check occlusion
  • cover vital dentine surfaces causing hypersensitivity
  • red. high tall thin cusps in occlusion (#)
  • review maintenance of OH
  • use matrix properly; over/under contoured
  • give self-care instruction

Inappropriate use material

  • inappropriate cavity
  • cavity treatment
  • mixing
  • placement
  • finishing

Using composite when pulpal margin in dentine

416
Q

Discuss material factors that can cause restoration to fail

A

Causes differ b/w materials
- #; too shallow amalgam
- corrosion, dissolution, chemical degradation
- wear; composite
- discolouration/staining
Some have much greater longevity (amalgam)

417
Q

Discuss auxiliary retention in amalgam restorations

A

Angled coves, vertical grooves, horizontal slots
Amalgapins; vertical into dentine 0.5mmW, 0.5-1mm D
Created using small diameter rose-head or 330
Entirely in dentine, care to avoid pulp
Replace need for pin-retained restorations

418
Q

Discuss ways to improve composite restorations

A

Proper isolation whenever possible; rubber dam
Work on clean tooth surface; clean w/ wet pumice slurry
Etch only area working on, wash thoroughly
Check for dry air flow in 3-in-1
- enamel completely dry
- dentine not desiccated
Rub primer and binding agent on surface; improve penetration
Centre LCU beam on area being cured
Small increments and shape appropriately to avoid cutting back
Polish to high shine using sequential grades polishing discs
Don’t paint unfilled resin/bond on surface, retain inhibited O2 layer

419
Q

3 main topical fluoride applications

A

Professionally applied
Rinsing solutions
Toothpaste

420
Q

Discuss professionally applied topical fluoride

A

Gel, solutions, varnishes

Red. caries 20-40%
Has to be controlled by professionals
Protocol for usage followed precisely

421
Q

Discuss topical fluoride rinsing solutions

A
  1. 2% 4nights/wk
  2. 05% daily (more suitable)

Red. caries 16-50%
NaF most widely used

422
Q

Discuss toothpastes as topical fluoride delivery

A

Cleaning, polishing, fluoride delivery

Abrasives, detergents, humectants, binding agent, preservative, active agents

423
Q

Discuss active agents of toothpaste

A

Fluoride: sodium monofluorophosphate

  • 1000-1450ppm
  • red. caries 15-30%

Anti-calculus: Na3PO4
- dec. calculates formation 50%

Desensitising: Sr 20%, KCl, 1.4% formaldehyde
Antibacterial: triclosan

424
Q

Discuss pre-eruptive and post-eruptive effects of fluoride deposition

A

Pre-eruptive

  • improve crystallinity
  • inc. crystal size
  • dec. acid solubility
  • more rounded cusps
  • improve fissure pattern

Post-eruptive

  • inhibit demineralisation
  • enhance remineralisation
  • inc. degree of remineralisation
  • inc. speed remineralisation
  • inhibit glycolysis (cariogenic bacteria); dec. acid production plaque
  • in plaque inhibit synthesis EC bacteria
425
Q

Discuss cariostatic mechanisms of fluoride

A

Form FA; larger crystal size inc. resistance to acid dissolution
- crystallisation of apatite occurs more rapidly

Change dimensions of HA; inc. resistance acid dissolution

Alters ability of bacteria to prod. acid and favours growth of some bacteria @ expense of others

Dec. glycolysis and dec. H+ gradient across cell wall
- this inhibits membrane ATPase which expels H+ from bacteria
— inhibit acid production and general energy metabolism of cells

426
Q

Discuss fluoride toxicity in relation to dentistry

A

Inc. incidence tooth mottling

Abscess formation around root dec. development of root leading to high level of tooth mottling

427
Q

Discuss fluorosis

A

Effects of excessive fluoride intake characterised by mottled enamel

Major effect at maturation
- proline rich materials remain thus mineralisation doesn’t inc
Localised inc. porosity
Opaque, chalky limes/patches
May take up stain
May be superficial (removed by attrition) or deep

428
Q

Discuss fluoride poisoning

A

Chronic

  • exostoses; bony growth on surface of Long bone
  • stiffness and pain in joints

Acute

  • nausea, epigastric pain, vomiting
  • limb spasms, tetany, convulsions
  • BP, pulse rate fall
  • respiration depressed
  • unconsciousness
429
Q

Discuss use and deficiency of dietary proteins

A

Source of AA; 30g/d

Use

  • growth
  • maintain N2 balance
  • recovery illness/starvation
  • synthesise Ig

Deficiency

  • kwashiorkor
  • marasmus
  • dec. Ig in saliva
430
Q

Discuss function of dietary carbs and fats

A

Fats

  • energy
  • EFAs; synthesis of lipid molecules
  • req. for fat soluble vitamins
  • some EFAs req. for calcification

Carbs; energy source

431
Q

2 classes of vitamins

A

Water soluble; B, C

Lipid soluble; D A K E

432
Q

Function and deficiency symptoms of vit B

A

Metabolic intermediaries
Regulators of RBC development

Deficiency

  • pallor of lips
  • cheilosis or red, shiny glossitis
  • megaloblastic anaemia (B12)
  • local inflammation
  • mucosa pale
433
Q

Function and deficiency of vit C

A

Powerful antioxidant

Deficiency

  • swelling, redness of interdental papillae
  • purplish inflammation and loss of epithelium
  • petechiae
  • dec. collagen synthesis (scurvy)
  • weakened PDL
  • gingivitis
434
Q

Function and deficiency of vit A

A

Essential for maturation and differentiation of epithelial tissues
Retinoic acid; growth factor

Deficiency

  • hyperkeratosis (mucosa)
  • hyperplasia of salivary glands; acini, ducts
  • red. salivary flow
  • atrophy of odontoblasts, osteoblasts
  • cleft palate
435
Q

Function, deficiency and excess vit D

A

Essential for normal absorption of Ca2+ and removal of bone

Deficiency

  • wide zone of pre-dentine
  • pre-dentine-calcified dentine border v irregular

Excess: hypercalcaemia, ectopic calcification

436
Q

Function and deficiency of vit K

A

Essential for synthesis of clotting factors

Deficiency: failure of blood to clot

437
Q

Discuss functions and deficiencies of essential minerals

A

Ca2+, PO43-

  • essential for calcification
  • poor calcification of teeth
  • osteoporotic changes

Mg

  • essential for calcification
  • susceptibility to caries

Fe
- anaemia: pail colour gingivae, infections, loss papillae on tongue

438
Q

Discuss causes, symptoms and treatment of xerostomia

A

Causes

  • dehydration
  • salivary gland pathology; Sjogren
  • conditions; stress, depression, renal failure, menopause, malnutrition, thalassemia major
  • drugs; nicotine, alcohol, cannabis, opiates, amphetamines
  • medication; anxiolytics, antidepressants, analgesics, antihypertensive
  • therapy; H and N radiation

Clinical

  • cheilosis
  • glossopyrosis, glossodynia
  • dysphagia, dysphonia, dysgeusia

Treatment

  • enhance flow; water, chew gum
  • alleviating products; artificial saliva/salivary substitutes
  • compensate for lack protection; topical fluoride, chlorhexidine
439
Q

What is alginate?

A

Irreversible hydrocolloid, elastic impression material

440
Q

Composition of typical alginate

A

Na/K alginate 12%
Diatomaceous earth (filler; body/strength) 70%
CaSO4 (cross-linking agent) 12%
Na3PO4/Na2CO3 (retarder) 2%
Sodium silicofluoride/fluorotitinate (pH controller) 4%
MgO (pH controller) ~3%

441
Q

Discuss the setting reaction of alginate

A

Function of retarder (Na3PO4/Na2CO3) and cross-linker (CaSO4)

H2O added

  • CaSO4 (sparingly soluble) -> Ca2+ + SO42- (slowly ionises)
  • Na3PO4 (v soluble) -> 3Na+ + PO43- (quickly ionises)

Then
- 3Ca2+ + 2PO43- -> Ca3(PO4)2 (insoluble)

After PO43- ions used, Ca2+ react w/ alginate to set material
- Na alginate + CaSO4 -> Ca alginate + Na2SO4

442
Q

Changes in state of alginate when water is added

A

Water added to alginate powder
Initially viscous paste formed
Then results in compliant elastic solid occurring through formation of chemical cross-links (via Ca2+)

443
Q

How does the alginate retarding agent suppress setting?

A

Na3PO4/Na2CO3

PO4/CO3 ions being used suppresses the reaction
Req. agent to inc. working T, w/o would set in bowl

444
Q

Discuss pH changes in the setting of alginates and the role of pH controllers

A

H2O + Na3PO4 -> alkaline (pH12)

During setting, pH initially dec. <3.5 then rises to pH~9 once set

Acidity/alkalinity of set gel give poor plaster/stone surface

pH controllers (sodium silicofluoride/fluorotitinate/MgO) dec. pH to near neutral (~8) to make compatible w/ casting materials 
- thus improve surface of resulting cast
445
Q

What is chromoclone?

A

Alginate w/ added pH indicators to show colour change (aid handling)

Water added change to purple
Mix thoroughly and completely until pink
Load into tray and wait
Light peach insert into mouth

446
Q

Discuss advantages of alginates

A

Setting behaviour; v good
- Na3PO4 suppress setting, material viscous paste while tray in mouth
- when setting beings; completed v quickly, min. T impression taking
Cheap, reliable

447
Q

Discuss disadvantages of alginates

A

Loss of H2O

  • continual shrinkage; req. immediate casting
  • poor dimensional stability
  • must be covered in damp gauze/sealing in bag (max few hrs)

Immersed in H2O

  • imbibes H2O causing swelling
  • shrinks as H2O soluble salts eluted
  • prolonged immersion in disinfectant impractical (unsolved problem)

Poor tear strength

Highly viscoelastic material

  • snap-removal technique req.
  • permanent deformation up to 1.5%
  • latter min. if undercuts not deep

Poor adhesion
-req. mechanical locking features and adhesive

448
Q

Discuss the dispensing of alginates

A

Density of ingredients differ

  • Have tendency to settle out in tub
  • Tub should be shaken before use, left to sit 2 mins (dust)
  • Silica particles (diatomaceous earth; filler) potentially hazardous
  • Most alginates now dust free

1:1 ratio
Room temp water
Mix 30s against side tub

449
Q

Discuss disinfection if set alginate impressions

A

Remove set alginate/tray from mouth
Rinse in tap water; remove saliva/blood
Immense in disinfectant (sodium hypochlorite) 10mins
Remove, rinse tap water
Wrap in damp gauze, seal in polythene bag (100% relative humidity)

450
Q

Discuss different types of alginates

A

Fast/regular/slow set
- vary amount CaSO4 and Na3PO4

Na alginate
K alginate
Mixtures of both

Triethanolamine alginate

  • dust free
  • triethanolamine salt of alginic acid
  • ball-mill alginate w/ small amount ethylene glycol
451
Q

What is agar?

A

Reversible hydrocolloid elastic impression material

452
Q

Properties of agar

A

Solid (gel) @ RT
Viscous liquid @ 60degrees
Revert back to gel on cooling
Gelling (setting) physical process

453
Q

Composition of agar

A 
Agar (colloid) 13-17%
Borates (strengthen) 0.2-0.5%
Potassium sulphates (accelerate) 1-2%
Thixotropic materials (wax) (filler) 0.5-1.0%
Water (dispersion medium) balance
454
Q

Discuss dispensing of agar

A

Dispensed in tubes; prevent H2O loss
Tubes out in water bath @ 60degrees to form viscous liquid
Transferred to 40 degree bath before use; so pt can tolerate
Material squeezed out onto special metal tray, seated in mouth

Cooled by water; circulated via cooling tubes attached on outer surface of tray

455
Q

Dis/advantages of agar

A 
Advantages
- once set up; easy to use
- cheap; more expensive cf alginate
- good surface detail
— fine detail recorded due to setting behaviour 
Disadvantages
- H2O loss (syneresis); req. immediate casting
- absorbs H2O (imbibition); distortion 
- compatibility w/ casting materials 
- poor tear strength; better cf alginate 
- high viscoelastic
— snap-removal technique
— permanent deformation up to 1%
456
Q

Define root caries

A

Caries at or apical to the CEJ that has undergone clinically apparent change

457
Q

Discuss epidemiology of root caries

A

W/ age more root surface exposed to oral environment
SA of exposed root inc,
More susceptible to caries
Problem among dentate older people

458
Q

Discuss aetiology of root caries

A

Progressive, destructive carious process; complex, multifactorial disease

Factors

  • root exposure
  • OH
  • diet
  • saliva
  • denture wearing
  • less F-
  • occlusion
  • cariogenic bacteria
459
Q

Discuss cariogenic microorganisms in relation to root caries

A 
S. mutans, sobrinus
Actinomyces
Lactobacillus
Yeasts
Prevotella
460
Q

Discuss classification of root caries by pattern of mineralisation

A

Soft; active

  • extensive demineralisation
  • no evidence of intact surface mineral layer

Leathery; active
- broad range of histological appearances

Hard; arrested
- uniform distribution of mineral throughout lesion

461
Q

Why can root caries not be classified by colour?

A

Little evidence showing correlation b/w colour and texture of lesion

462
Q

Discuss clinical classification of root caries

A

Active
- well defined, soft, yellowish/light brown, covered by visible plaque

Slowly progressing

  • brownish black
  • leather

Arrested

  • shiny, smooth, hard
  • no microbial deposits
463
Q

Histological appearance of root caries

A

Demineralisation of cementum extending into dentine

464
Q

Outline the non-invasive and invasive methods of root caries management

A

Non-invasive; active -> inactive by preventive methods

  • no treatment; observe
  • OHI, dietary advice
  • pharmaceutical methods

Invasive

  • drill and fill
  • caries debridement, Lesion re-contouring
  • sealant
  • ART
  • abrasive technique
  • chemo-mechanical caries removal
  • lasers
  • ozone therapy
465
Q

Discuss clinical problems w/ management of root caries

A 
Enamel critical pH 5.2-5.7
- root substance 6.0-6.7
Lesions may spread subgingivally
High organic content of dentine
Proximity to dental pulp
Moisture control
Carious surfaces -> plaque retention -> gingival oedema
466
Q

Discuss the pharmaceutical methods of root caries management

A

Fluoride; aid remineralisation, prevent demineralisation active -> inactive

  • rinses
  • 12000ppm gel 4 month intervals + home care
  • varnishes 3 month intervals

Chlorhexidine
- varnish

Triclosan; bacteriostatic, inhibit fatty acid synthesis

Chlorhexidine and thymol; varnish

467
Q

Discuss invasive management of root caries and difficulties associated w/ it

A

Excision or infected, necrotic, partially decalcified dentine and replacement w/ biologically acceptable material w/ suitable properties

Intra-coronal restoration

  • RM/GIC
  • composite
  • amalgam

Difficulties

  • isolation; RD
  • access
  • lesions encircling whole neck
  • subgingival margins
  • application of material to approximal surfaces
468
Q

Discuss the importance of early detection of carious lesions

A

Destruction occurs in months/yrs not days/wks
Lesions arrestable in early stages
Progression to cavitation not inevitable
Prevent w/ relatively simple measures
Small lesions remineralise more readily
Remineralised lesions more resistant

469
Q

Rational for restoring teeth

A 
Cavity won’t calcify from base
Trap plaque
Restore integrity of tissues by eliminating plaque traps
Seal (no material gives perfect seal)
- preventive methods still important
Eliminate pain, discomfort 
Improve appearance
470
Q

Discuss cavity design for amalgam

A 
Brittle; weak in thin sections
Margin angles >70
Mechanical retention
- undercuts
- grooves
- slots
- pins
471
Q

Discuss cavity design of composite

A

Aesthetic
Micro-mechanical retention to acid-etched enamel
Adhesion to dentine via bonding agents
Weaker cf amalgam

472
Q

Discuss cavity design for GIC

A 
Tooth coloured inf. cf composite 
Adhesive to tissues
Release F
Weaker cf composite 
Ideal for cervical abrasion cavities 
Good replacement for dentine
473
Q

Discuss cavity design for gold restorations

A

Malleable and ductile
Strong; protect weak cusps
Mechanical retention from cavity features and cement

474
Q

Ideal properties of impression material

A

Pleasant odour, taste, aesthetic
Adequate shelf life for storage and distribution
Freedom from toxic constituents
Economically commensurate w/ results obtained
Easy to use; min. equipment
Setting characteristics meet clinical requirements
Satisfactory consistency and texture
Readily wets oral tissues
Elastic properties w/ freedom from permanent deformation
Adequate strength not break/tear on removal
Dimensional stability over T and humidity range
Compatibility w/ cast/die materials
Accuracy in clinical use
Readily disinfects w/o loss of accuracy

475
Q

Discuss uses of elastomer impression materials

A

Due to strength and dimensional stability

  • produce accurate replica teeth and supporting tissue
  • construction of full/partial denture, crowns, bridges, inlays
476
Q

Discuss the dispensing of impression materials

A

2 paste

  • fluid in unset, cross linked in set
  • 3D network crosslinked molecules
  • 1/both pastes contain polymer

2 separate tubes
2 tubs of putty or putty and tube

Double barrel cartridge

  • avoid incomplete mixing
  • prevent air bubbles
477
Q

How does setting reaction of impression materials affect dimensional stability?

A

Addition: no byproduct thus no setting shrinkage

Condensation: small molecule byproduct thus setting shrinkage

478
Q

Discuss the viscosities of elastic impression materials

A

Range depends on amount of filler and MWt of polymer
Putty, heavy, medium, light-bodied, wash

Wash/light least amount filler; Putty max. filler

479
Q

Why can’t light-bodied/wash impression material be used by itself?

A

As little filler doesn’t have strength; tear easily on removal
Records fine details

480
Q

Discuss impression technique for putty and wash

A

Twin mix/1 stage

  • wash syringed around prepared teeth
  • putty loaded into tray, inserted immediately after syringing wash

Double impression/2 stage

  • putty used to take impression before preparation
  • after preparation wash syringed around teeth and putty impression reinserted over wash
481
Q

Discuss dis/advantages of putty and wash technique

A

Advantage; record fine detail

Disadvantages

  • 1 stage; materials mixed simultaneously
  • 2 stage; takes longer for 2 impressions
482
Q

Discuss impression technique for dual viscosity

A

Heavy and light pastes

Heavy extruded into tray
Light syringed around teeth or placed on heavy in tray
Tray seated and material set
Light flows into undercuts, records fine detail
Heavy acts as support

483
Q

Discuss components of condensation silicones

A

Poly(dimethyl siloxanes)

Base paste

  • silicone polymer w/ terminal OH
  • inert filler

Catalyst paste (can be liquid)

  • tetraethoxy othrosilicate (cross linking agent)
  • dibutyl tin dilaurate (catalyst)
  • inert filler
484
Q

Discuss setting of poly(dimethyl siloxane)

A

Condensation silicone

Ethanol byproduct

485
Q

Discuss advantages and disadvantages of poly(dimethyl siloxanes)

A

Advantages

  • stronger, better dimensional stability cf alginate
  • more elastic cf polyethers, polysulphides
  • tear strength and elongation @ break adequate

Disadvantages
- shrink in air (condensation crosslinking) ~0.3-0.5%
- hydrophobic; detergents incorporates to confer wettability
— May expand in disinfecting solutions depending on hydrophilic agent
- mouth dry as possible
- erratic setting behaviour w/ liquid catalyst
- short shelf life w/ liquid catalyst

486
Q

Discuss the components of polyvinyldimethylsiloxanes

A

Base paste

  • silicone polymer w/ terminal vinyl group
  • inert filler

Catalyst paste

  • silicone oligomer w/ Si-H groups (cross linking)
  • platinum salt catalyst
  • inert filler
487
Q

Discuss dis/advantages of polyvinyldimethylsiloxane impression material

A

Addition silicone

Advantages

  • best dimensional stability cf all impression
  • elastic recovery v good; more elastic cf polysulphids, polyethers

Disadvantages

  • free H2O in plaster/stone reacts w/ unreacted Si-H releasing H, porous material
  • %elongation, tear strength generally < condensation Si; both adequate
  • setting impaired when handled w/ natural rubber gloves (poison catalyst)
  • hydrophobic; detergents incorporated
  • mouth fairly dry
  • hydrophilic addition silicones May expand due to hydrophilic agents
  • poor shelf life, long set
488
Q

Discuss components of polyether impression materials

A

Base paste

  • polyether polymer (terminal ethylene-imine groups)
  • fillers
  • plasticisers
  • pigments
  • flavourings
  • triglycerides

Catalyst

  • initiator; cationic starter sulphonium tetraborate salt
  • fillers
  • plasticisers
  • pigments
489
Q

Function of fillers, plasticisers and triglycerides in polyether impression materials

A

Fillers: high rigidity of impression and help maintain dimensional stability

Plasticisers: adjust the viscosity

Triglycerides: inc. intrinsic viscosity

  • resilience coupled w/ flowability under pressure
  • viscosity dec. w/ inc. shear force
490
Q

Discuss the setting reaction of polyether impression materials

A

Cationic (addition) reaction via ring opening

491
Q

Discuss dis/advantages of polyether impression materials

A

Advantages

  • good dimensional stability in air
  • clean to handle, odourless
  • quick setting (cf polysulphides), reliable

Disadvantages

  • permanent deformation; recovers slowly and not completely
  • dimensional stability in H2O/H2O vapour swells
  • 50% elongation @ break (poor), v stiff Young’s 90x105 Pa; tear
492
Q

Discuss components of polysulphide impression materials

A

Base

  • polysulphide polymer (Thiokol S-S)
  • filler; ZnS, TiO2
  • plasticiser; phthalate ester

Catalyst

  • PdO2 (cross linking)
  • Filler (base)
  • plasticisers (base)
  • Sulphur ~1%
  • stearin or oleic acid
493
Q

Describe the setting reaction of polysulphide impression materials

A

Base reacts w/ PdO2 via condensation reaction w/ H2O byproduct

494
Q

Dis/advantages of polysulphide impression materials

A

Advantages

  • strongest
  • elongation @ break 500%

Disadvantages

  • dimensional stability; shrink 0.1-0.2%
  • slow setting
  • dirty to handle, unpleasant smell
  • elastic recovery not as good cf silicone and polyether
495
Q

Discuss non-elastic impression materials

A

Impression plaster

  • mucostatic (doesn’t displace soft tissue)
  • no trays req.
  • material sets hard
  • edentulous cases only

Impression compound

  • poor thermal conductivity/flow
  • doesn’t reproduce undercuts
  • mucocomoressive (displace B and L tissues)
  • high viscosity; full depth of sulcus req. to support denture

ZOE

  • brittle when set
  • accurate in thin section
  • initial low viscosity and pseudoplasticity
  • mucostatic
496
Q

Discuss which impression materials do not meet ideal properties

A

Pleasant odour, taste, aesthetic: polysulphide
Adequate shelf life for storage, distribution: all
Freedom from toxic irritants: (old) polyether
Easy to use: silicones, polysulphide/ether, agar
Setting characteristics meet clinical req.: polysulphide
Readily wets oral tissues: silicones
Elastic properties w/ freedom from permanent deformation
- alginate, agar, polysulphide/ether
Adequate strength
- alginate, agar, polyether
Dimensional stability: alginate, agar, polyether
Compatibility w/ cast and die: addition silicone, agar
Readily disinfects w/o loss of accuracy
- condensation silicone, polyether, alginate, agar

497
Q

Reasons for making/uses of study casts

A

Show pt what you mean when talking about treatment
Permanent record of teeth @ various stages of treatment
Examine occlusion when pt not there
Examine teeth and supporting tissues in detail; making dentures
Add wax to reshape teeth and show pt change (diagnostic wax up)
Construct better fitting impression trays for dentures (special trays)
Legal record of why you did work

498
Q

What is post-damming?

A

Adding wax post. to U impression tray to prevent excess alginate flowing down soft palate/throat

Dependent on not over filling and having good mix (not too runny)

499
Q

If wax has been added to a impression tray to modify it how do we insure frenum attachments are still recorded?

A

Making V shape in wax where labial and buccal frenulum attachments are

500
Q

Discuss pt management when taking alginate impressions

A

Pt sitting up (can be lying flat)
Position self so can see where alginate is going
- i.e. stand in front of pt, alginate not going down throat
Eye protection
Bib

Gag reflex

  • do lower 1st
  • post dam upper
  • distraction techniques
  • don’t overload
501
Q

Discuss technique for taking alginate impression

A

Have correct tray; fit, size, modifications

Fill tray to border
Seat in mouth (watch for excess)
Massage lips/soft tissues around tray to create functional impression of buccal and labial sulci
Remove
Rinse, disinfect (10 mins), rinse
Wrap in damp gauze and paper towel, package in bag and label

502
Q

Define occlusion and articulation

A

Occlusion: static position, described by Angles classification of incisal, molar or skeletal relation

Articulation: movement of teeth against each other, dynamic descriptive
- lateral, protrusion, retrusion

503
Q

Describe Centric Relation and Intercuspal Position

A 
Centric relation (1)
- bilateral unstrained position of mandible where condyle disc is in most sup. ant. position in glenoid fossa

Intercuspal position (2)

  • most U and L teeth in contact
  • relatively stable; altered by changing tooth shape w/ restorations/wear
504
Q

Describe positions 3, 4, 5 on Posselt’s diagram

A

3: edge-to-edge incisal relationship
4: reverse overjet of incisors

5

  • max protrusion
  • not stable as muscle controlled; muscles will tire, position changes
505
Q

Discuss r and h on Posselt’s diagram

A

r Resting Position

  • position mandible adopts @ rest
  • teeth slightly apart (~4mm) when occlusal plane U teeth horizontal
  • complete denture; want 4mm opening @ incisors from ICP (freeway space)

h Habitual Opening

  • muscles of mastication avoid slide from CR-ICP
  • mandible closes straight into ICP
506
Q

Discuss points II and III on Posselt’s diagram

A

II
- max. point of pure hing opening on mandible from CR (RCP)

III

  • max. opening of mandible
  • influenced by muscle tone, tiredness, head position
  • lat. pterygoid, some extent temporalis
507
Q

Define Bennett angle and Bennett movement

A

Angle
- formed b/w Sagittal plane and average path of advancing condyle as viewed in horizontal plane during lat. mandibular movement

Movement
- bodily lat. movement/lat. shift of mandible resulting from movements of condyles along lat. inclines of mandibular fossae during lat. jaw movement

508
Q

Compare ant. and post. guidance

A

Ant.; at level of teeth

  • tooth movement is influenced by tooth-tooth contact
  • most important thing is how steep are cuspal inclines on teeth
  • NOT NECESSARILY ANT TEETH

Post.; at level of condyles

  • no influence on movement by teeth (complete denture)
  • influenced by shape of glenoid fossa, how condylar head and disc move over it
  • alters choice of cusp heights and angles for post. teeth on denture
509
Q

Discuss mutually protected occlusions

A

Canine guidance

ICP = RCP

Multiple even contacts in ICP on all teeth w/ tighter contacts post. and lighter ant.
Complete disclusion
- of all other teeth on lat. excursion using canines only
- of post. teeth in protrusion using even contacts on all ant. teeth

510
Q

Discuss balanced articulation

A

In lat. movement teeth are in contact on non/working sides

Only used in removable prosthodontics as postulated this occlusion will stabilise dentures during chewing cycles

Natural dentition: non-working side contacts/interferences thought to be detrimental to functioning occlusion

511
Q

Discuss building rapport w/ child pt

A

Greet child and adult in waiting room; establish who adult is
Ensure correct pt info
Ask what pt prefers to be called
Lead to clinical area; talk about non-dental stuff
Anxiety: reassure how easy today will be
Observe gait, physical appearance, size, interaction w/ parent

512
Q

Common c/o of child pt

A

Double/shark teeth: 1s develop slightly behind As
Eruption cyst/pain: fluid filled sac, blueish hue
Gingival operculum: gum covers D O table; inflammation, pain, food trap, plaque
Supernumeries/mesiodonts: ortho opinion -> XLA
Ant. open bite: digit/dummy sucking -> stop sucking, ortho

513
Q

Distinguish b/w reversible and irreversible pulpitis

A

Reversible

  • short duration pain
  • sharp pain
  • sweet/hot/cold stimuli
  • remove stimuli, remove pain
  • analgesics help
  • remove dentine

Irreversible

  • longer duration
  • dull throbbing ache
  • spontaneous pain
  • wake child
  • analgesics don’t help
  • pulpotomy
514
Q

Distinguish b/w low, med, high caries risk

A

Low

  • caries free, favourable family history
  • good OH, diet, motivations
  • fluoride toothpaste/water

Med: 1/2 new lesions/yr

High

  • 3/+ new lesions/yr
  • ortho treatment
  • chronic illness
  • social factors
515
Q

Eruption dates of 1ry dentition

A

Begins 6/12 +/- 6/12

6-12/12: As, Bs
14/12: Ds
18/12: Cs
24/12: Es

516
Q

Compare anaesthesia and analgesia

A

Anaesthesia: loss of all sensation to circumscribed area by depression of excitation of nerve endings or inhibition of conduction in peripheral nerve

Analgesic: loss of only pain sensation (nociception)

517
Q

Define LA

A

Drug which reversibly prevents transmission of nerve impulse in region applied w/o affecting consciousness

518
Q

Structure of LA

A

Lipophilic, aromatic portion

Amide/Ester linkage

Hydrophilic amine portion

519
Q

2 types of LA

A

Amides

Esters

520
Q

Compare amide and ester LA

A 
Amide: only type available in UK dental 
- stable in blood 
- metabolism: hepatic, slower than Ester
— liver disease inc. risk toxicity 
- lidocaine, prilocaine, articaine, bupivacaine, mepivacaine,

Ester

  • metabolism: pseudocholinesterase (plasma), rapid
  • v short duration of action
  • inc. allergic potential
  • procaine (novocain), benzocaine (topical gels)
521
Q

Mechanism of action of LA

A

LAs are weak bases: have both charged and uncharged molecules

Uncharged molecules cross membrane into nerve cell
Equilibrium rebalanced intracellularly; produce more charged molecules
Charged molecules bind inactivated VGNa+C, block Na+ entry
Shift equilibrium so more charged molecules available

522
Q

Discuss factors affecting mechanism of LA

A

Environmental pH and drug pKa

LA weak base: pKa ~8-9
Physiological pH 7.4

pKb > pH favour ionised form (less effective)
Infections red. pH, red. effectiveness LA
LA w/ lower pKb more effective

523
Q

4 constituents of LA

A

LA agent
Vasoconstrictor: Ad, felypressin
Reducing agent: stabilise vasoconstrictor by preventing oxidation of Ad
Isotonic solution: Ringer’s solution

524
Q

What are vasoconstrictors and why are they added to LA?

A

Additives that control blood flow by red. vessel diameter

Reasons

  • red. local bleeding (local infiltration)
  • less systemic absorption (red. toxicity)
  • prolong duration
525
Q

Contraindications for vasoconstrictors in LA

A

Ad: unstable angina, controlled arrhythmias
- inc. cardiac output, inc. blood pressure, risk arrhythmia (red. plasma K)

Felypressin: late stage pregnancy

526
Q

Discuss 3 common LA agents

A

Lidocaine 2%

  • widely used, gold standard
  • highly effective, low toxicity, good tissue tolerance
  • available w/ Ad

Prilocaine 3%

  • citanest
  • felypressin: less effective preventing haemorrhage

Articaine 4%

  • t1/2 20min
  • rapid metabolism; part in plasma
527
Q

Equipment req. for LA

A

Cartridge
Syringe
Needle

528
Q

Discuss LA cartridge

A

Cylinder (clear plastic/glass), plunger, cap
Contents, conc., expiry, manufacturer, batch no.
2.2/1.8ml

529
Q

Discuss LA syringe and needle

A

Syringe: accept cartridge

Needle
- SS, beveled 
- short 25mm; Long 35mm
- gauge (thickness)
— 30: fine, infiltration
— 27: thick, block
530
Q

Discuss the safety syringe

A

Avoid need to re-sheath
Safety lock

Blue: 30 gauge (fine), 25mm (short) needle; infiltration
Yellow: 27 gauge (thick), 35mm (long) needle; block

White handles disposable

531
Q

Administration routes of LA

A

Topical

  • mucous membranes
  • before infiltration
  • benzocaine (gel); lidocaine (spray)

Infiltration: submucosal injection act on local nerve endings, porous bone

Regional

  • cortical plate too thick
  • inject @ site where nerve unprotected by bone
  • block nerve trunk
532
Q

Compare duration of lidocaine and prilocaine

A

Lidocaine w/ Ad

  • pulpal 45-1h
  • soft tissue 3-5h

Prilocaine w/ VC

  • pulpal 1h
  • soft tissue 2-3h
533
Q

7 factors affecting duration of LA

A 
Environmental pH
Drug pKa
T of diffusion from needle to nerve
T of diffusion away from nerve
Nerve morphology
Conc.
Lipid solubility
534
Q

Steps to interpretation of X-ray

A 
Good quality X-ray
Good viewing conditions 
Systematic approach
- decide if anatomy, artefact, pathology
- describe area of interest

For pathology need differential diagnosis

535
Q

Rating system for X-rays

A

NRPB/RCR

1: excellent
- no errors of exposure, positioning, processing
- not <70%

2: diagnostically acceptable
- some errors of EPP but don’t detract from diagnostic utility
- not >20%

3: unacceptable
- errors of EPP which render X-ray diagnostically unacceptable
- not >10%

536
Q

Factors affecting reviewing of X-rays

A

Luminance
Resolution
Contrast ratio
DICOM

537
Q

Discuss normal anatomy of maxilla and mandible seen in X-rays

A 
Max.
Ant
- nasal floor, teeth
- Y line of Ennis (nasal floor joins maxillary sinus)
Post.: max. sinus, teeth
Mand.
Ant. 
- trabecular pattern, tooth
- ID canal, mental foramen 
Post. 
- trabecular pattern, ID canal
538
Q

Discuss radiographic classification of caries

A

R0: no radiolucency
R1: radiolucency <1/2 through enamel, don’t record if doubtful
R2: radiolucency >1/2 enamel, not into dentine
R3: <1/2 through dentine to pulp (outer 1/2)
R4: >1/2 through dentine to pulp (inner 1/2)

539
Q

Factors affecting appearance of caries on X-ray

A 
B-L thickness 
Superimposed images of tissues
X-ray not paralleled 
Incorrect exposure factors
Cervical burnout 
Mach band
540
Q

What are cervical burnout and Mach band?

A

Cervical burnout

  • radiolucency just above alveolar crest, invagination of roots
  • mimic appearance of root caries
  • due to varying density of tissues

Mach Band

  • optical illusion
  • areas at junction of differing tissue density appear radiolucency
  • disappear by covering radiopaque area
541
Q

9 factors must be mentioned when describing lesion from X-ray

A 
Site
Size/extension
Shape
Margin: well/poorly defined
Cortication (white line around): well/poorly
Radiolucent/paque/mixed
Loculation: uni/multilocular
Expansion 
Effect on adjacent structures
542
Q

Most important CN in dentistry

A

CNV: trigeminal

543
Q

Function of trigeminal

A

Sensory: face, sinuses, teeth
Motor: muscles of facial expression

544
Q

Branches of trigeminal

A

V1: ophthalmic
V2: maxillary
V3: mandibular

545
Q

Branches of V2

A

Post., mid., ant. sup. alveolar
Greater and lesser palatine
Nasopalatine

546
Q

Branches of V3

A 
Inf. alveolar nerve 
Incisive 
Mental 
Lingual
Mylohyoid
Long buccal
Auriculotemporal
547
Q

Function of branches of V2

A 
Post. SAN
- 8 and 7, DB and P cusp 6
- adjacent B gingiva, mucosa, periodontium, B alveolar bone
Mid.: MB cusp 6, premolars; “
Ant.: canines, incisors; “

Greater palatine: P mucosa and bone adjacent pre/molars
Lesser: soft palate and uvula

Nasopalatine: P mucosa and bone adjacent canines, incisors

548
Q

Function of branches of V3

A

Inf. alveolar: mandibular teeth and alveolus

Mental: gingiva, mucosa premolars-incisors
- skin, mucosa lower lip and chin

Lingual: ant. 2/3 tongue, mucosa, gingival floor of mouth

Long buccal: B gingiva and mucosa premolars-molars

549
Q

Differences in infiltration in maxilla and mandible

A

Can’t be performed on mandible (except incisors)

Maxilla

  • cortical bone B side thin
  • LA B mucosa, infiltrate to pulp

Mandible

  • cortical bone too thick
  • IANB
550
Q

Discuss palatal infiltration

A
  1. 2ml P mucosa D to tooth of interest
    - anaesthetise ant. to 3 region (nasopalatine supplies ant.)
    - 10-15mm from gingival margin (fleshiest part; least pain)

Uncomfortable due to tightly bound mucosa

8s: infiltrate ant.; greater palatine foramen lies ant.
Ant.: nasopalatine block preference

XLA: B and P infiltration
FIL: B (main supply) sufficient

551
Q

Dis/advantages of infiltrations

A

U and L incisors

Advantages

  • simple
  • block all nerve endings in area

Disadvantages

  • must diffuse through bone
  • infection spread if inflamed area infiltrated
  • limited zone anaesthesia/injection
552
Q

Regional block dis/advantages

A

Advantages

  • widespread anaesthesia; block all downstream
  • avoid infected areas

Disadvantages

  • more difficult
  • excessive soft tissue anaesthesia
  • potential haemorrhage (bleeding disorder pt)
  • potential nerve trunk injury
553
Q

What is the pterygomandibular space? Boundaries of it

A

Anatomical landmark used for ideal positioning of IANB

Post.: parotid
Lat.: ramus
Medially + inf.: medial pterygoid 
Sup.: lat. pterygoid
Ant.: buccinator
554
Q

Preparation steps for infiltration

A

Requirement: procedure req.; pain and/or blood control
Safety
- medical history: contraindications, allergy, medications
- anxiety
Treatment
- XLA: block all nerves
- FIL: main supply only
Nerves: specific nerves determine infiltration/block
Consent: why, risks, benefits
Prepare syringe
- correct length + gauge
- check: expiry, no damage, clear, no bubbles

555
Q

Discuss aspiration in relation to LA

A

Avoid intravascular injection
Safety syringe self aspirating
- -ve pressure draws blood into cartridge if in vessel
Check cartridge before delivery

556
Q

Steps to performing infiltration

A

Apply topical

  • small amount gel in dappens pot
  • cotton pledget/roll
  • clean + dry before
  • retract lip, apply
  • wait 3-4mins
Retract soft tissues
Entry
- gentle, direct continuous movement 
- depth B sulcus, above tooth
- stretch tissues taut (pain-free)
Aspirate 
- push plunger then release 
- check no blood
Deliver: slow, even pressure; 1ml/30s
Withdraw 
- slow, release pressure
- needle on bracket, sheath 
- check pt
557
Q

What must be recorded in pt records after LA?

A 
Type of LA
Vasoconstrictor + conc.
Vol
Batch no.
Injection; site, needle
Pt reaction
558
Q

4 ways to make LA as painless as possible

A

Appropriate topical
Hold mucosa taut
Slow entry
Slow delivery

559
Q

When would a IANB be used?

A

Alveolar bone too thick (mandible)
Avoid area infection
Wider area anaesthesia req. w/ 1 injection

560
Q

Discuss anatomical landmarks for IANB

A

Palpate coronoid notch

  • use non-dominant thumb
  • greatest concavity ant. border ramus

Palpate internal oblique ridge
- feel medially then pull laterally

Pterygomandibular raphe: fold connect U->L

Surface triangle

  • midday b/w internal oblique and raphe
  • surface triangle: raphe, oblique line, U teeth

Locate nerve: needle over opp. premolars

Tissue layers

  • penetrate mucosa, connective tissue, muscle
  • contact bone, withdraw ~2mm
561
Q

Technique for IANB

A 
Apply topical 
Identify landmarks 
Positioning
- thumb in deepest part coronoid notch
- needle over opp. premolars 
Entry
- mucosa taut, insert 15-25mm
- contact bone, pullback 
Aspiration and delivery
- slow pressure; 2ml/60s
Withdraw: slowly
562
Q

Common errors when administering IANB

A

Too straight: don’t hit bone, in parotid gland -> facial palsy

Indirect technique (too angled)

  • hit bone v early
  • realign needle (remain in) then swing round to premolars
563
Q

Which area is not anaesthetised in IANB?

A

B soft tissues premolar-molar region

Req. long buccal block

564
Q

Discuss articaine infiltration

A 
Used to avoid IANB
Also called intraseptal/supracrestal 
Buccal infiltration
27 gauge, short needle
5mm below tip papilla, 3mm from gingival margin
565
Q

Discuss long buccal block

A

Can do B sulcus D to tooth of interest

True block

  • ant. aspect ramus
  • palpate coronoid notch, insert for bony contact
  • withdraw; deliver 0.2-0.5ml
566
Q

Discuss mental nerve block

A

Deliver to mental foramen
Inserted through reflected mucosa aiming for bone region b/w premolar apices
1.5ml

567
Q

Discuss palatal blocks

A

Greater palatine

  • anaesthetise soft tissue and hard palate 8-3
  • short needle
  • greater palatine foramen D aspect U7
  • 0.2ml

Nasopalatine

  • short needle
  • near incisive papilla
  • <0.2ml
568
Q

Epidemiology of dental disease in children

A

Decay: 1/3 5yo; ~50% 15yo
>10% children Wales XLA due to decay
Teenagers consume 50% more sugar than recommended
DMFT 0.8 12yr; dmft 0.9 5yo

569
Q

Factors that can help decision making in child pt

A

Know chil

  • careful questioning
  • see regularly
  • social/medical/dental circumstances
  • developmental stage
  • family dynamics
  • appearance
  • school

Growth and development

  • infant record book
  • developmental milestones
  • speech, language, motor skill, socialisation development
  • dental

Disease risk

  • past disease, current status
  • family/social/medical history
  • OH, diet
570
Q

Possible parental and child problems associated w/ treating child

A

Parent

  • attitude towards OH
  • extended care arrangements for child
  • financial/social/personal barriers to bringing child

Child

  • fears and expectations
  • medical conditions
  • ability to cope w/ treatment
571
Q

Difference between cleaning, disinfection and sterilisation

A

Cleaning: physical removal microbes, not necessarily killing

Disinfection

  • red. no. viable microorganisms may not kill some (viruses, spores)
  • instrument safe to handle

Sterilisation: killing and removal all microorganisms

572
Q

Outline risk assessment for instruments and recommendation for each group

A

High (critical)

  • penetrate soft tissue
  • contact bone
  • enter normally sterile tissue/blood
  • close contact break in skin/mucous membrane
  • recommendation: sterilisation or single use

Med. (semi-critical)

  • contact non-intact skin/mucous membrane/body fluid
  • recommendation: sterilisation or high level disinfection

Low (non-critical)

  • intact skin, not in contact w/ pt
  • disinfection
573
Q

Outline decontamination facilities

A

Dirty room/zone

  • instrument washing and rinsing sinks
  • ultrasonic bath
  • inspection area
  • thermal washer disinfector

Clean room/zone

  • inspection area
  • steriliser (autoclave)
  • package and storage areas

Separate hand basin, PPE storage in both clean and dirty
Air flow: clean -> dirty
Instruments: dirty -> clean

574
Q

Discuss pre-sterilisation cleaning

A

Aim to dec. bacterial load

Manual
Automated
- ultrasonic bath (cleaning only)
- thermal washer disinfector; loaded if free from cement and tolerate

Blood: corrosive to stainless steel; don’t let instrument dry out
Full PPE

575
Q

Discuss ultrasonic bath

A 
Mental instruments only
Only cleans instruments
Typically 20-40 degrees, 3 mins
Rinse, drain, dry
Titanium and stainless steel separately
Inspect w/ magnifier
576
Q

Discuss thermal washer disinfector

A

Preferred method
More efficient red. bacterial load
Enhanced safety
40-50min cycle

Prewash 35degree, main wash, rinse, thermal disinfection 90degree 1 min, post disinfection rinse, dry

577
Q

Discuss sterilisers and sterilisation cycles

A

B

  • air removal by vacuum sterilisation; vacuum pump
  • for most instruments incl. hollow and lumens
  • not: heat liable, single use

S

  • air removal; vacuum sterilisation; successive steam pulses
  • loads specified by manufacturer
  • not: heat liable, single use

N

  • non-vacuum; air displaced passively
  • for: solid
  • not: wrapped devices, hollow devices, devices w/ lumen, heat liable, single use

Temp: 134-137
Pressure: 2.25
Time: 3 mins

578
Q

Discuss instruments that require special considerations for cleaning

A

Endodontic files

  • single use
  • reusable: 1 pt if tracked through decontamination

Single use

  • steel burs
  • saliva ejector
  • matrix bands
579
Q

How can LA complications be avoided?

A

Medical and drug history

  • previous problems w/ LA
  • systemic conditions
  • medications which may interact
  • anxious/nervous pt
580
Q

Risk groups for LA complications

A

Elderly
Children
Medically compromised

581
Q

General types of unwanted effects due to LA

A

Physical trauma: needle or self injury of anaesthetised tissues
- warn pt

Chemical trauma: altered sensation (high LA conc.)

Bleeding
Spread of infection

Inappropriate deposition site: IV, parotid
Toxicity: safe dose
Allergy
Medical condition: liver disease, arrhythmia, unstable angina, haemophilia
Drug interactions

582
Q

General 4 causes of unwanted LA effects

A
  1. Injecting inappropriate solution
  2. Injecting too much solution
  3. Injection into wrong site
  4. Bad luck
583
Q

Discuss allergy as LA complication

A

More likely to be ester LA

Reducing agents (LA w/ Ad): pt w/ sulphur allergy
Latex allergy (cartridge plunger): latex free plunger
Ad: supersensitivity (tachycardia)
- history of rash/breathing difficulties following LA taken seriously

584
Q

Drugs that may interact w/ LA

A

Interact w/ LA agent

  • beta-adrenergic blockers
  • Ca2+-C blocker
  • anticonvulsant
  • antimicrobial
  • benzodiazepines

Intact w/ vasoconstrictor

  • beta-adrenergic blocker
  • calcium channel blocker
  • diuretics
  • CNS: anti-Parkinson’s, antidepressant, GA, IVDU
585
Q

Discuss possible problems w/ injecting too much LA

A

LA OD -> toxicity
- esp. children; toxic dose weight related

Early signs: excitability; inhibitory function of brain first to be depressed
Followed by CNS depression -> unconsciousness
If v large dose; death due to respiratory depression

Effects are cumulative; can’t switch LA after max. dose 1 given

586
Q

Discuss why hepatic function is important in LA side effects

A

Liver is main organ involved in amide LA metabolism
Conditions affecting hepatic function must be considered when assessing max. dose
- drugs, disease, age (65yo liver function 1/2 that of 25yo)

587
Q

Main sites that can cause problems if LA injected into

A

Intravascular (arterial, venous)
Intraneural
Parotid gland

588
Q

Discuss injecting intravascularly as problem of LA

A

May cause

  • pain
  • localised blanching
  • cranial effects: transient blindness, double vision, temporary deafness
  • systemic: heart; tachycardia, arrhythmia

Use of aspirating syringes: red. chance inadvertent injection into vessel

589
Q

Discuss injecting into parotid gland as problem of LA

A

Facial nerve traverses parotid gland; facial nerve palsy

  • unable to close eyelid on affected side
  • paralysis resolve as LA wear off

Ensure needle contact bone pre-administrating IANB
Eye protection until motor function restored

590
Q

Discuss problems w/ intraneural LA injection

A

Injection into nerve trunk can cause damage due to needle trauma and physical/chemical damage

May cause

  • long term anaesthesia; loss sensation
  • paraesthesia
  • dysaesthesia; pain
591
Q

Discuss possible problems that may be due to bad luck injecting LA

A

Penetration on both sides blood vessel (IANB) bleeding
- if affects muscle (medial pterygoid) post-injection trismus

Contact nerve (electric shock) painful 
- don’t inject there
592
Q

Strategies to red. LA complications

A 
Take good medical/drug history 
Use aspirating syringe 
Limit use of regional blocks
Use min. vol. LA possible
Inject appropriate solution slowly (1ml/30s)
593
Q

Aims of X-ray quality assurance

A

Produce diagnostic radiography of high standards

Red. radiation dose to pt & staff

594
Q

How can X-rays be assessed?

A 
Image quality
Pt dose &amp; X-ray equipment
Personnel &amp; training
Working procedures
Audits: compare to gold standard
595
Q

Discuss how image quality of Xray can be assessed

A

Subjective: problematic

Contrast
Not pixelated/blurry
Subject in frame

596
Q

Why is quality assurance of X-ray important?

A

Red. no. repeats
Inc. efficiency
Determine all sources of errors to allow correction
Red. costs
Keep dose as low as reasonably practicable

597
Q

5 general types of errors that occur to X-ray

A 
Preparation
Positioning 
Exposure factors 
Processing 
Resolution
598
Q

Discuss preparation & positioning errors of X-rays

A

Preparation

  • geometric accuracy
  • ghost imaging: from opp. side, blurred, appear higher
  • lead apron/thyroid cover

Positioning

  • cone cut, beam moving (maintenance)
  • not sitting properly
  • overlapping teeth: misaligned horizontal
599
Q

Discuss exposure errors of X-rays

A

kV, mAS, T
Cervical burnout
Underexposed

600
Q

What are line pairs per mm?

A

Measure of resolution
No. line pairs that can be distinguished per mm

More line pairs = higher resolution
Human eye sees 12LP
- digital 10LP
- conventional 100LP

BDS 2 (4 decks)

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