Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What happens if odontoblasts die?

A

Eburnoid: atubular calcification formed by pulpal cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Explain pulpitis

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

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

A

Blue: ant.
Red: BW
Yellow: post.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What are the 2 main types of O radiographs?

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

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What is the focal trough/plane of a pan?

A

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

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
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
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What is a cephalometric radiograph?
Standardised reproducible radiograph that assesses relation of teeth to jaw and jaw to facial skeleton Taken using a cephalostat
26
What are the uses of cephalometric radiographs?
``` Ortho/orthognathic surgery; Skeletal/soft tissue abnormalities Treatment planning Monitoring progress Assess treatment results ```
27
What are the 2 types of radiographs?
1. Digital: in/direct | 2. Conventional: manual, automatic
28
Describe solid state radiograph sensors
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)
29
Describe advantages and disadvantages of SSS X-rays
Advantage: instant Disadvantage: cost, bulky, difficult to position
30
Describe how phosphor plate sensors are processed
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
31
What factors are important when viewing radiographs?
``` Display; LCD, CRT Resolution Contrast ratio Luminance DICOM; digital imaging and communication in medicine - standard, more info than jpeg ```
32
What is the active layer of film X-ray sensors?
Emulsion layer; silver halide crystals
33
What happens to silver halide crystals when exposed to X-rays?
Become sensitised
34
What is film processing dependent on?
``` Protected from light Chemicals; liquids and vapours Temp and time Film washed and dried Regular QA (sensitometry) checks ```
35
Explain the processing of film sensors
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
36
Define composite
2/+ materials put together w/ each contributing to overall properties
37
What are the main uses of composites?
``` Filling material FS Endodontic post and cores Luting agent Indirect restorations ```
38
What are the 3 phases of direct composites?
1. Organic matrix 2. Inorganic filler 3. Coupling agent
39
What is the function of the organic matrix of composites?
Monomer phase | Plastic monomer/resin material that polymerises to form a continuous phase, binding filler particles via coupling agent
40
What is the function of the inorganic filler phase of composites?
Reinforcing particles and/or fibres dispersed in matrix
41
What is the function of the coupling agent in composites?
Bonding agent promotes adhesion b/w filler and resin
42
Describe the organic matrix phase of composites
Chemically active component(s) which polymerise to form rigid polymeric material when cured Monomer is viscous fluid which cures via FR, addition polymerisation
43
What monomers does the organic matrix of composites contain?
BisGMA: v viscous liquid UDMA: alternative, less viscous
44
What does the high viscosity of the monomers in the organic matrix mean for the composite?
Makes unworkable | The addition fillers further inc. viscosity thus contain diluent monomers (viscosity controllers)
45
What additives are in the organic matrix of composites?
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
46
What are the main 5 advantages to using fillers?
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
47
Why is the refractive index of filler and resin important for composites?
Must match closely to avoid scattering light otherwise fill depth of cure will not be achieved on LC Has major effect on colour
48
What are the main types of fillers?
Conventional/traditional: macro Hybrid/small particle hybrid Microfine
49
Describe traditional fillers
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
50
Describe microfine fillers
<1microm Colloidal silica Initially inc. viscosity but incorporation method improved Can be polished: v smooth surface finish
51
What is the problem w/ microfine fillers?
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
52
Explain the incorporation method of microfine fillers to ensure adequate filler loading
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
53
Describe hybrid fillers
Large filler particles (<10microm) and small amount colloidal silica (0.01-0.05microm) particles
54
Describe small particle hybrid fillers
Average particle size <1microm | Range 0.1-6.0microm
55
Advantages and disadvantages of hybrid fillers
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
56
What is the advantage of a nanofilled composite?
Strength of hybrid | Polishing finish of micro
57
Compare the uses of microfilled and hybrid filled composites
Micro: ant. restorations due to lower filler loading; properties compromised Hybrid: post. restorations due to higher filler loading; better mechanical properties
58
What is the advantage of using coupling agents?
Filler and resin must bond to have acceptable mechanical properties Improved wear resistance of final restoration
59
Why must coupling agents be used?
Organic resin hydrophobic, filler hydrophilic (surface -OH) thus need agent to bond
60
How does silane coupling agent work?
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
61
Why is a stable adhesive bond b/w filler and resin required?
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
62
What are the 3 methods of curing composites?
1. Heat: indirect, in/onlays 2. RT: BP, dihydroxyethyl-p-toluidine 3. LC: DHPT + camphorquinone
63
Discuss advantages and disadvantages of LC composite
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
64
At what range of wavelengths do visible light activated composites cure?
450-500nm
65
Describe the process for LC
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
66
Why do darker shades require longer curing time?
Pigments absorb more light thus must cure for longer
67
What are the 4 main types of LC units?
1. Tungsten-Quartz-Halogen 2. LED 3. Plasma-Arc 4. Argon Laser
68
Discuss Tungsten-Quartz-Halogen LC units
``` 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 ```
69
Discuss LED LC units
``` Slimline Cordless; rechargeable Less lat. heat production (cf halogen) Long lasting, low wattage Narrow emission spectrum; 460-480nm ```
70
Discuss plasma arc LC units
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
71
Discuss argon laser LC units
``` High energy Highest intensity Emit at single wavelength (490nm) V expensive Warning signs required ```
72
What are the main advantages of composite restorations?
1. Excellent aesthetics 2. Less tooth tissue removed 3. Command set (LC) 4. Some cavity's too small for amalgam (chip on incisal edge)
73
Name 6 disadvantages of composites
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
74
Why is shrinkage a problem for composite restorations?
2-3% by vol Problems for marginal adaptation Breakdown of bonds to tooth tissues Can result in recurrent caries
75
Discuss water uptake as a disadvantage of composites
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)
76
Discuss staining of composites
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
77
Why is wear a problem for composites?
Abrasive, fatigue, corrosive | W/ T resin matrix wears, filler particles protrude through surface giving dull appearance
78
Why is biocompatibility an issue for composites?
Composite components and breakdown products released Uncared resin can lead to - cytotoxicity and delayed hypersensitivity from eluted materials - oestrogenic effects
79
Discuss the oxygen inhibition layer of composites
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
80
Discuss silorane
``` New composite material Polymerisation shrinkage <1% Lower shrinkage stress/strain Lower H2O absorption Mechanical properties 'within range' of other composites ```
81
Discuss bulk fill
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
82
What are the advantages to using adhesives?
Better aesthetics Conservation of tooth tissue Reinforcement of weak tooth structure Red. marginal leakage
83
What are the ideal requirements of an adhesive?
Provide high bond strength to enamel and dentine Immediate and durable bond Prevent ingress of bacteria Safe and simple to use
84
Discuss the problems encountered w/ bonding composite to enamel
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
85
How are the problems encountered when bonding composites to enamel combated?
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
86
What are the main effects of the acid-etch technique?
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
87
Describe application of resin after acid-etch bond technique
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
88
Why is it important to have adhesion b/w resin and dentine?
Retain restoration in cavity; dentine hydrophilic, resin hydrophobic Eliminate marginal/internal gaps to prevent bacterial microleakage
89
What problems are faced when bonding composite to dentine?
When cut, fluid pumped through dentine tubules giving wet surface Inorganic HA crystals broken, collagen stretched, torn and smeared over surface giving smear layer
90
What is the smear layer?
Layer of denatured collagen and debris covering surface and weakly bound to dentine Contaminated w/ bacteria (caries) and cutting debris
91
What is required for strong bonding of resin to dentine?
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
92
What are the 3 essential components to dentine bonding agents?
1. Conditioner (etch) 2. Coupling agent/primer (prime) 3. Sealer (bond)
93
Describe dentine conditioner
Acid solution; stronger, more pronounced effect Remove/modify smear layer; acid-base reaction w/ HA Rinsed w/ water Demineralised dentine surface left
94
Describe the dentine coupling agent
Acts as adhesive bonding dentine to resin | Has bi-functional molecule such as HEMA
95
What must the dentine coupling agent do to achieve strong bonding?
Penetrate and saturate dentine tubules to reasonable depth thus must be dissolved in solvent (ethanol, acetone) Seeks out and displaces water
96
Describe the dentine sealer
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
97
What is the hybrid layer of dentine?
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
98
Discuss the biocompatibility of dentine bonding agents
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
99
What are some of the causes of adhesive bond breakdown and what can this result in?
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
100
Discuss different tooth surfaces as habitats for microbial flora
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
101
Discuss mucosal surfaces in mouth as habitat for microorganisms
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
102
Discuss how saliva can affect microorganism growth
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
103
Discuss how GCF can alter microflora growth
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
104
Describe factors of non-specific immunity in the mouth
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
105
Describe factors of specific immunity in the mouth
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
106
Discuss Strep. mutans in relation to dental caries
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)
107
Discuss gram-+ rods and filaments in relation to dental caries/plaque
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
108
Discuss gram negative rods in relation to dental plaque and caries
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
109
Most important and prevalent fungi in mouth?
Candida albicans
110
Discuss presence of viruses in the mouth
Herpes simplex: most common Hepatitis, HIV: present in saliva of asymptomatic pt Coxsackie and papilloma: lesions, cancer
111
Define occlusion
Static relationship b/w 1/+ max. teeth and 1/+ mand. teeth | Teeth in contact w/ each other (when clenched)
112
Ortho definition of occlusion
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
113
What is the maximum intercuspation position?
Position w/ most tooth-tooth contact for that individual's occlusion Importance: restorations must harmonise w/ existing occlusion (conformative occlusion)
114
Define articulation
Dynamic gliding contacts b/w 1/+ max. teeth and 1/+ mand. teeth
115
What is Posselt's envelope?
Diagram of sagittal movement of mandible | Resting, intercuspal, incisal contact, max. protrusion, max. opening, habitual closing
116
How is dynamic articulation classified?
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
117
Why can group function articulation be problematic?
Lat. loading can # thin walls of restorations | Use composite to build up ramp on 3s to keep ICP and restore canine guidance
118
Explain working side and non-working side articulation interference
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
119
Define plaque
General term for complex microbial community embedded in matrix of salivary and bacterial components (biofilm) and found on teeth
120
Outline the development of plaque
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
121
What 4 things is accumulation of plaque dependent on?
1. Adhesion 2. Growth 3. Removal via physical forces 4. Plaque interactions
122
Describe the structure of mature dental plaque
Tooth surface Acquired pellicle Early colonisers: Strep. sanguinis, oralis, mitis; Actinomyces so Fusobacterium nucleatum Late colonisers: Porphyromonas gingivalis
123
Discuss function of establish plaque from bacterial perspective
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.
124
Describe function of dental plaque from host perspective
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)
125
What is the drop in pH after sugar intake dependent on?
``` Type, amount carb available Bacteria present Salivary composition and flow Other food ingested Thickness and age plaque ```
126
Discuss resting plaque pH and account for differences in it
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
127
Discuss the fluctuation in plaque pH
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
128
Discuss the ecological plaque hypothesis
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
129
Discuss metabolism of carbs in relation to plaque
Glycolysis: glc->pyruvate Pyruvate fermented by plaque bacteria to lactate Homofermentative bacteria >90% lactic acid Heterofermentative bacteria formic, propionic, acetic, succinc acids
130
Discuss the 4 concepts in cariogenic bacteria that allow for their survival
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)
131
Discuss IC polysaccharides in dental plaque
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
132
Discuss EC polysaccharides in dental plaque
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
133
Define primary, secondary, residual, rampant and hidden caries
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
134
Define active and arrested caries
Active: considered to be progressing Arrested: no longer progressing
135
Define white spot and brown spot lesion
White spot: first sign visible by naked eye w/ strong white light Brown spot: inactive white spot discoloured by uptake of dye
136
Functions of saliva
``` Neutralise acids Prevent demineralisation/enhance remineralisation Recycle ingested F to mouth Discourage bacteria growth Proteins sustain enamel surface Protective, coating, lubrication ```
137
Discuss importance of Ca and PO in saliva
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
138
Discuss smart bioactive molecules in saliva
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
139
Describe Stephan curve
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
140
What is the critical pH?
5.5 | pH at which saliva is no longer supersaturated wrt Ca, PO this dissolution takes place; net loss of enamel
141
Define acid-base cement
Formed on mixing powder and liquid, which, through acid-base reaction prod. solid matrix that binds mass together
142
Discuss ideal properties of acid-base cement
``` 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 ```
143
Discuss general setting of acid-base cements
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
144
3 factors affecting setting of acid-base cements
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
145
How can acid-base cements be classified?
``` Type Application Powder Liquid Bonding ```
146
Classify acid-base cements by type
``` Zinc phosphate Zinc polycarboxylate Zinc oxide/eugenol (ZOE) Glass ionomer cements (GICs) Calcium hydroxide Ethoxybenzoic acid (EBAs) ```
147
3 classifications of acid-base cement by application
I: luting II: restorative or lining III: lining or base
148
Classify acid-base cements by chemical bonding
Phosphate bonded: zinc phosphate Polycarboxylate: zinc polycarboxylate, GICs Phenolate: CaOH, ZOE, EBA
149
Classify acid-base cements by liquid base
Water based: zinc phosphate, zinc polycarboxylate, GIC | Oil based: CaOH, ZOE, EBA
150
Classify acid-base cement by powder
Zinc oxide: zinc polycarboxylate, zinc phosphate, ZOE, CaOH2, EBA Ion leachable glass: GIC
151
Discuss composition of zinc phosphate acid-base cement
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
152
Outline setting of zinc phosphate
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
153
Discuss advantages and disadvantages of zinc phosphate
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
154
Discuss properties of zinc phosphate
Depend on power:liquid especially for strength Compressive strength 40-140MPa
155
Uses for zinc phosphate cement
Primary: luting for restorations and ortho due to strength Secondary: thermal insulating base, temp. restorative
156
Discuss composition of zinc carboxylate cement
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
157
Discuss setting of zinc polycarboxylate
Complex Min reaction b/w ZnO and -COOH of PAA Freshly mixed cement is pseudoplastic (shear thinning) Inter and intramolecular crosslinks formed
158
Discuss dis/advantages of zinc polycarboxylate
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
159
Uses of zinc polycarboxylate
Primary - luting (adhesive potential) - thermal insulating base (low irritancy) Secondary - luting ortho bands - intermediate and temporary restorations
160
Discuss composition of conventional GICs
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
161
Discuss importance of tartaric acid in GICs
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
162
3 stages of GIC setting
Dissolution Gelation Final maturation
163
Discuss dissolution of GICs
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
164
Discuss gelation stage of GIC setting
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
165
Discuss final maturation of GIC setting
Ratio bound:unbound H2O inc. Strength inc. Take up to 24h; GIC needs to be protected immediately after placement
166
Importance of water balance in GICs
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
167
Discuss chemical bonding in GIC
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
168
Discuss how GIC can inhibit caries
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
169
Discuss biocompatibility of GIC
Bioactive Low irritant despite low pH H+ movement constrained by high MWt polymeric anion Restricts diffusion down dentinal tubules
170
Discuss dis/advantages of GICs
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
171
Uses of GICs
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
172
Discuss high viscosity GICs
``` 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
173
Discuss composition cermets
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
174
Discuss properties and uses of cermets
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
175
Discuss composition resin modified GIC
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
176
Discuss dis/advantages of RMGICs
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
177
Uses of RMGIC
``` Cavity lining In GIC-composite laminate technique Ant. restorative Restorative in deciduous teeth Luting cement ```
178
Discuss composition of polyacid modified composites/compomers
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
179
Discuss properties of PAMC/compomers
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
180
Uses PAMC/compomers
``` Low stress situations Proximal and abrasion cavities Restorations primary teeth Long term temporary restorations permanent teeth Recently, luting cement ```
181
Discuss giomers
Composite resin + pre-reacted GI particles as filler Have F release, recharge of F w/ sup. properties of composite Restorative, luting, FS
182
Discuss new development being made in acids for GIC
Polyvinyl phosphoric acid More reactive Improved strength, moisture resistance Less acid soluble
183
Requirements for caries detection
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
184
Define classifications of caries lesion
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
185
Discuss special investigations into caries lesions
X-rays: BWs Sensibility testing (response to stimuli - test vitality) - temp. - electrical pulp tester - text cavity (drill)
186
Discuss sequence for accessing caries lesions
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
187
Discuss the aims and equipment used for enamel preparation for caries lesions
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
188
Define anatomical extent ands histological depth of carious lesion
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
189
Discuss sequence and equipment used for dentine removal
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
190
Define cavity retention and cavity resistance
Retention: resist displacement in direction of insertion Resistance: resist displacement in any other direction
191
Compare stepwise and atraumatic restorative technique
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)
192
Define dentine-pulp complex
Dynamic tissue that responds to mechanical, bacterial and chemical stimuli as functional unit
193
Compare pulp and dentine
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
194
Importance of dentine being a living tissue
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
195
Discuss response of dentine to caries and treatment
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
196
Compare reactionary dentinogenesis and reparative dentinogenesis
Reactionary: req. stim. of existing odontoblasts Reparative: req. recruitment progenitor cells from cell rich layer of pulpal tissue
197
How does dentine respond to cavity preparation?
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
198
What is a consequence of the fluid shifts during cavity preparation?
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
199
What is the problem w/ current equipment used for assessing caries?
No non-invasive tools to assess pathological condition or severity of inflammation within pulp
200
What factors affect pulp healing?
``` Drill speed Use of coolant Operator pressure Extent of cavity preparation Unnecessary iatrogenic removal of dentine Extensive, prolonged use of acid-etch ```
201
Discuss pulp capping
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
202
How can tissue engineering aid pulp-dentine complex?
Application of advanced biological systems w/ therapeutic agents that control inflammatory response of pulp-dentine complex while inducing remineralisation of dentine
203
Define cavity liner
Permanent, intermediate restorative material lining cavity applied before placement of restorative
204
3 types of cavity liner
Varnish Cavity liner Cavity base
205
What factors impact cavity liner choice?
``` Position Size and depth Condition of tissues OH Restorative being used ```
206
Role of cavity liners
To be - protective - palliative; relieve pain - therapeutic to vital dentine - barrier to penetration through tubules Protect pulp
207
Discuss cavity varnishes
``` Coat layer painted on cut surface; 2-5microm Seal dentine Red. diffusion through tubules - barrier to penetration of chemicals Dec. microleakage No strengthening property ```
208
Composition of cavity varnishes
Natural resins; copal Synthetic resins; polystyrene Solvent; alcohol, acetone, ether Some: Ca(OH)2 and/or ZnO
209
Discuss suspension liners
Non-setting Ca(OH)2 - Ca(OH)2 suspension in H2O 20-25microm thick layer Methyl or ethyl cellulose can be added for strength
210
Discuss cavity liner
``` Thin coat <0.5mm Seals exposed dentine Promotes health of pulp - adheres to tooth structure - antibacterial Materials: Ca(OH)2, ZOE, ZnO non-eugenol ```
211
Discuss cavity base materials
``` 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 ```
212
Composition of Ca(OH)2 based cements
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
213
Discuss setting reaction of Ca(OH)2 based cements
Acid-base reaction | Disalicylate reaches w/ Ca(OH)2 and ZnO to form chelate-calcium disalicylate
214
Discuss handling of Ca(OH)2 cements
= 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
215
Discuss dis/advantages of Ca(OH)2 cements
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.
216
Discuss uses of Ca(OH)2 cements
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
217
Discuss composition of ZOE cements
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)
218
Discuss setting reaction of ZOE cements
Acid-base reaction ZnO w/ eugenol forms zinc eugenolate (chelate complex) H2O initiates reaction and is by-product - will reverse in excess H2O
219
Discuss handling of ZOE cements
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
220
Discuss dis/advantages of of ZOE cements
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)
221
Discuss reinforced ZOEs
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
222
Uses of ZOE cements
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
223
Compare Ca(OH)2 and ZOE cements
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
224
Discuss ethoxy benzoic acid cements
``` 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
225
Discuss ZnO non-eugenol cements
Other oils will form cements w/ ZnO Use w/ resin composites and materials formed by polymerisation If pt allergic to eugenol
226
Discuss use of visible light cure resins as cavity liners
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
227
Discuss calcium silicate based or MTA cements
Mainly used for endodontics High strength Alkaline pH Bioactive; pulp repair
228
What are the preventative materials?
``` Toothpaste, mouthwash Topical F - varnishes - gels - supplement tablets, solutions Sealants ```
229
Discuss F gels
``` 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
230
Discuss acidulated phosphate fluoride (APF) composition
pH 3 NaF 2% HF 0.34% Othrophosphoric acid 0.98% Hydroxyalkyl cellulose (thickening)
231
Discuss fluoride varnish
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 ```
232
Discuss pit and fissure sealants
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
233
Discuss resin sealants
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
234
Discuss GIC sealants
``` 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 ```
235
Discuss other sealants
RMGIC: better retention and wear cf GIC but lower cf resin based Compomers: similar to resin-based
236
Define probing/pocket depth and attachment loss
Probing depth: distance (mm) from gingival margin to base of sulcus Attachment loss: distance (mm) from cementoenamel junction to base of sulcus
237
Discuss the periodontal tissue
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
238
Changes to gingiva in gingivitis
Colour change; v red Change in consistency Changes in contour; triangular papilla not sharp Plaque and calculus in contact w/ inflamed tissue
239
Discuss the sulcus
In health 1-3mm deep Gingival sulcus: space b/w free gingivae and tooth Junctional epithelium forms base
240
Discuss junctional epithelium
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
241
Discuss function and adaptations of junctional epithelium
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
Discuss periodontal ligament
``` Connective tissue around and attach teeth to alveolar bone Fibres - alveolar crest - horizontal - oblique - apical fibres - inter radicular ```
243
What are Sharpey’s fibres?
Portion of principle PDL fibres embedded in cementum (tooth side) and alveolar bone (bone side)
244
Discuss cementum
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
Define periodontal pocket
Gingival sulcus that has deepened due to loss periodontal attachment to >3mm depth
246
Compare gingivitis and periodontitis
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
Discuss the epidemiology of periodontal disease
``` 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
Discuss the prevalence of gingivitis
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
What are periodontal diseases?
Inflammatory reaction to accumulation plaque at gingival margin Can lead to tooth loss Divided into gingivitis and periodontitis
250
4 main classifications of periodontal disease
Gingival diseases Chronic periodontitis Aggressive periodontitis Periodontitis as manifestation of systemic disease
251
Discuss gingival diseases
Dental plaque-induced gingival diseases | Non-plaque induced gingival lesions
252
Discuss chronic periodontitis
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
Discuss aggressive periodontitis
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
Risk factors of periodontal disease
``` 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
Predominant features of both gingivitis and periodontitis
Immune and inflammatory reactions to plaque bacteria
256
Describe role of plaque in the progression of gingivitis
Inflammation develops immediately Gram +ve bacteria accumulate supragingivally After 24h changes evident, inc. blood flow - bacterial mix more complex - gram -ve colonise subgingivally
257
5 stages of periodontal disease progression
``` Health: pristine condition Initial lesion: clinically healthy Early lesion: early gingivitis Established lesion: chronic gingivitis Advanced lesion: chronic periodontitis ```
258
Discuss the initial lesion stage of periodontal disease
``` 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
Discuss early lesion stage periodontal disease
7-14d Predominantly lymphocytes and neutrophils Inc. vascularity Collagen destruction; create space for inflammatory infiltrate
260
Discuss established lesion of periodontal disease
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
Discuss advanced lesion of periodontal disease
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
Discuss the host response to the biofilm
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
Discuss the host-microbial balance in periodontitis
Healthy gingiva consistently feature inflammatory cells In response to continuous presence of bacteria in the crevice Defence mechanisms stop progression to periodontitis
264
Discuss the pathogenesis of periodontal disease
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
Discuss role of PMNs in inflammatory response
Predominant defence cell in crevice Migrate from vessels into gingival tissues in response to stimuli (chemotaxis) 1st line
266
Discuss cytokines role in inflammatory response
Proteins secreted by PMNs, macrophages that transmit signals Inc. inflammation Stim. bone resorption Stim. collagen breakdown (fibroblasts)
267
Discuss role of prostaglandins in inflammatory response
Produced by macrophages Cause vasodilation Stim. secretion inflammatory mediators PGE2: stim. fibroblasts to produce MMP and osteoclasts
268
Discuss role of MMPs in inflammatory response
Matrix metalloproteinases Family enzymes that breakdown proteins Collagenase Produced by fibroblasts and PMNs MMP levels inc. as tissue destruction occurs in periodontal disease
269
Discuss bone resorption in periodontitis
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
Define fissure sealant
Material placed in pits/fissures in order to prevent/arrest development of caries; obliterates fissures and removes sheltered environment favourable for bacteria
271
What are the pt and tooth indications for FS?
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
Discuss the 3 materials used for FS
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
FS procedure
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
Discuss the cost effectiveness of FS and the 3 factors it depends on
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
What is a preventative resin restoration?
Composite/GIC restoration w/ remaining pits/fissures sealed w/ FS When stained fissure is caries lesion just into dentine in 1 area
276
Describe the diagnosis technique for determining whether PRR req.
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
Dis/advantage to PRR
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
Materials for PRR
Unfilled resin Filled resin GIC
279
PRR procedure
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
8 reasons for restoring 1ry teeth
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
Compare 1ry and permanent molars
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
Considerations in cavity preparation in 1ry dentition
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
5 factors that impact on decision to restore 1ry dentition
1. Developmental stage of child 2. Caries risk assessment 3. OH 4. Parent compliance 5. Child compliance
284
6 materials used for restoring 1ry molar
1. Amalgam 2. Composite 3. GIC 4. RMGIC 5. Compomer/PAMC 6. Stainless steel crown
285
Dis/advantages of amalgam 1ry molar restoration
+ - ease of manipulation - durability - relatively low cost - red. technique sensitivity - not moisture sensitive - - aesthetics - perceived safety - need mechanical retention = more tooth tissue removed
286
Dis/advantages of composite 1ry molar restorations
+ - aesthetics - minimal tooth removal - - polymerisation shrinkage - technique sensitive - good isolation/pt compliance - time consuming - not suitable large, multiple surface restorations
287
Dis/advantages GIC and advantage RMGIC
+ - 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
Dis/advantages SSC
+ - durable - inexpensive - minimal sensitivity - full coronal coverage - - aesthetics
289
Outline principles involved in preparation of O cavity in 1ry molar
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
Outline procedure for proximal 1ry amalgam restoration
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
Indications for SSC
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
Contraindications for SSC
1ry molar close to exfoliation w/ more than 1/2 root resorbed Pt w/ known nickel allergy or sensitivity
293
Discuss SSC procedure
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
What is the Hall technique?
Method for managing carious 1ry molars w/o LA, tooth preparation or caries removal
295
Outline the Hall technique procedure
``` Assess tooth shape, contact points Sit child slightly upright Protect airway Size crown Cement crown Fit crown ```
296
Macroscopic structural properties of enamel
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
Microscopic properties of enamel
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
What method is used to study crystallite alignment and direction?
Synchrotron X-ray diffraction
299
General macroscopic mechanical properties of enamel
Hardness: Moh scale 5-8 Compressive: 350 MPa Shear: 90 MPa Tensile: 10 MPa
300
Discuss elastic modulus and hardness of enamel
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
Discuss # toughness of enamel
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
Discuss structure-function relationship of enamel w/ regards to enamel microstructures
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
Discuss structure-function relationship of enamel w/ regards to protein remnants
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
Compare #/failure of restored vs unrestored tooth
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
Factors have to be considered to decide optimal cavity shape
Min. reduction of tooth tissue to preserve max. tooth Material used Geometry of cavity Keep stress level low to avoid # of restoration
306
Factors impacting on geometry of cavity
Size and type of tooth Type of cavity: non/undercut Material: amalgam, composite, GIC, porcelains, gold
307
Discuss where stress is and where cracks propagate in bonded and non-bonded materials
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
Define macroscopic and microscopic cavity modifications
Macro: large scale modification, using burs Micro: small scale, chemically
309
Define cavosurface angle and line angle
Cavosurface: angle b/w cavity wall and surface of tooth Line angle: angle b/w any 2 surfaces of tooth; mesiolingual
310
Discuss macro and microscopic preparations for amalgam cavity
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
Macroscopic features of composite/GIC cavities
Enamel margin bevel - remove grossly unsupported enamel - inc. SA bonding - better marginal seal + same as amalgam
312
Microscopic features of composite cavity
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
Microscopic GIC cavity preparations
Conditions - 10% polyacrylic/citric acid - remove smear layer - prepare surface for Ca2+ bonding
314
Define screening
Simple test performed on large number of people to identify those most likely to develop specific disease
315
Why are PD assessments performed?
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
How is PD health assessed?
``` Gingival colour, contour, recession Pocket depth Bleeding on probing Tooth mobility Furcation involvement X-rays ```
317
Describe healthy PD tissue
``` Pink Stippled; firmly adherent to underlying bone No bleeding Little recession No mobility Pocket depth <3mm ```
318
What problems are found when measuring PD disease?
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
Define false pocket and true pocket
False: inc. probing due to gingival swelling/overgrowth, no attachment loss True: inc. probing due to loss of PD attachment
320
Describe the BPE procedure
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
How does PBE take place for children?
Check 6 teeth - UR6 UR1 UL6 - LR6 LL1 LL6 If 7-12; use codes 0-2 12+ all codes Only if compliant
322
Dis/advantages of BPE
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
Discuss the 6 point pocket chart (6PPC)
``` 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
Common probing errors for PBE
``` Interference from calculus on tooth/root Presence of overhanging restoration Incorrect angulation of probe Amount of pressure applied to probe Misreading probe ```
325
PBE codes 0-4
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
PDE codes X and *
X: edentulous or 1 functioning tooth | *: furcation involvement
327
Discuss alveolar bone
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
Discuss bone loss in relation to radiographic PD assessment
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
What are X-rays used to visualise in PD assessment?
Bone levels Root length and shape Furcation Restorative status; filling, caries, RCT
330
Discuss different types of X-ray in relation to PD assessment
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
Define amalgam and dental amalgam
Amalgam: when Hg mixed w/ another metal Dental: Hg + Ag-Sn alloy
332
Compare composition low Cu and high Cu dental amalgams
``` 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
Function of Ag and Sn in amalgam
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
Function of Cu and In in amalgam
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
Function of Zn, Hg, Pd in amalgam
Zn: scavenger, dec. oxidation other metals Hg: activates reaction Pd: inc: tarnish and corrosion resistance, strength
336
Different composition combinations possible of amalgams
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
2 possible particle shape combinations of amalgam
Lathe cut | Spherical
338
Discuss lathe cut amalgam particles
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
Discuss spherical amalgam particles
Produced by atomising molten alloy in inert atmosphere Acid wash to inc. reactivity 5-50microm size
340
Compare lathe-cut and spherical particles
``` Spherical particles: Req. less Hg 40-45% Less mixing T Lower condensation pressures Harden more rapidly Smooth surface ```
341
How can amalgams be classified?
Cu content: high and low Cu alloys Zn content: Zn free and containing Alloy: binary, ternary, quaternary Shape: lathe-cut, spherical, admix
342
Discuss trituration if amalgam
Carried out in mechanical mixer 3000rpm 5-20s Powder mixed w/ 40-50% Hg - higher amount low Cu alloy
343
Discuss how to tell correct trituration has occurred
Under: dull, dry, crumbly Properly: shiny, smooth, separates from capsule in single mix Over: shiny, hot, wet, sticks to capsule
344
Discuss condensation of amalgam
``` Packed incrementally into cavity Condensed to: - remove excess Hg - prevent voids - give optimal marginal adaptation ``` Final Hg content - 45% lathe-cut - 40% spherical
345
Difference b/w packing of lathe-cut and spherical amalgams
Lathe: small condenser tip w/ high pressure Spherical: large condenser tip w/ low pressure
346
Discuss setting of amalgam
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
Discuss the phases of conventional/low Cu alloys
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
Discuss admired high Cu alloys
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
Discuss single phase high Cu alloy
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
Discuss the finishing of amalgam restoration
Carving - function size and shape alloy - spherical better surface finish Burnishing - removal residual Hg - better margins Polishing - necessary(?) - aesthetics
351
Discuss dimensional changes of amalgam during setting
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
Factors that inc. shrinkage of amalgam
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
Discuss dimensional changes of amalgam restoration after setting
Delayed expansion Zn containing alloy contaminated w/ H2O, H2 gas evolved causing expansion and possible pain if pressure on pulp
354
Discuss tarnish of amalgam
Surface discolouration Formation black silver sulphide - can be polished off No long term problems or effect on clinical lifetime
355
Which phase in low and high Cu alloys most prone to corrosion?
Low Cu: gamma 2 (Sn7-8Hg) phase - products: tin oxides and chlorides High Cu: eta (Cu6Sn5) phase - products: tin oxides and chlorides, CuCl
356
Discuss different types of corrosion in amalgam
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
Discuss mechanical properties of amalgam
High compressive strength Tensile 50-60MPa Good wear resistance Hg content critical to strength
358
Compare mechanical properties of low and high Cu alloys
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
Discuss disadvantages of amalgam
``` 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
Discuss factors affecting marginal seal of amalgam restorations
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
Discuss use of varnishes for marginal seal of amalgam
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
Discuss how creep can affect marginal seal of amalgams
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
Discuss factors affecting quality of amalgam restoration controlled by manufacturer and dentist
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
Discuss different forms Hg
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
Discuss the toxicity of Hg
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
Discuss amalgam tattoos
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
Factors affecting choice of DM in paediatrics
``` Clinical situation, National guidelines Tooth structure, cavity depth Longevity Toxicity Pt compliance - procedure length - moisture control Parents consent ```
368
Dis/advantages of amalgam
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
Dis/advantages of composite
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
Dis/advantages of GICs
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
Dis/advantages RMGIC
``` 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
Dis/advantages of PAMC/compomers
Advantages - F release delayed - longevity - coloured restorations (paediatrics) - greater strength cf GIC, RMGIC Disadvantage - shrinkage - exothermic - bonding req.
373
Discuss stainless steel in preformed metal crowns/SSCs
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
Discuss dis/advantages SSCs
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
List dental materials in order of inc. pH
``` 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
List dental materials in order of dec. pulpal irritation
Zn phosphate GIC Zn polycarboxylate ZOE, CaOH2
377
List dental materials in order of inc. solubility
``` Composite GIC, Zn phosphate Zn polycarboxylate ZOE CaOH2 ```
378
Define thermal conductivity and thermal diffusivity
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
List dental materials in dec. thermal conductivity, diffusivity and expansion
Conductivity Amalgam>>composite=Zn phosphate>GIC>ZOE=dentine Diffusivity Amalgam>>composite>ZOE>Zn phosphate>GIC=dentine Expansion Composite>ZOE>amalgam>GIC=tooth
380
What is gypsum?
Calcium sulphate dihydrate (CaSO4)2H2O | Mineral found in nature
381
General uses of gypsum products
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
What do manufacturers convert (CaSO4)2H2O into? What does this form?
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
What are alpha and beta hemihydrates? Compare structure
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
Uses of plaster
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
Uses of improved/stone
Dies - models of mouth - replica individual teeth - construction crown and bridges Where max. strength essential for dentate casts Study casts
386
Composition of gypsum products
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
How do accelerators/retarders affect setting T?
Inc./dec. solubility of gypsum
388
Discuss gypsum accelerators
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
Discuss retarders
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
Discuss chemistry of setting of gypsum products
(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
Discuss setting mechanism of gypsum products
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
Discuss factors affecting setting of gypsum products
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
Discuss the setting expansion of gypsum products
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
Discuss properties gypsum products
``` 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
Case for prevention of decay in children
Tooth decay most common dental disease affecting children Poor OH impact on general health, wellbeing, growth, development Largely preventable Huge burden on NHS
396
Discuss caries risk assessment in children as preventative risk strategy
Caries risk assessment - think about disease - lost etiological factors in order of importance (presence of caries most important) - identify risk category
397
Describe the 3 risk categories of caries in children
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
Outline the 3 principles of prevention of dental caries in children
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
Outline 1ry preventative methodologies for children
``` 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
Outline 2ry preventative methodologies for children
``` BWs Occlusal caries - clinically into dentine; repair - fissure system only; PRR Approximal/smooth surface - enamel only; fluoride, dec. sugar, inc. brushing ```
401
Outline 3ry preventative methodologies for children
``` Restoring decayed tooth - restore function - prevent further disease progression XLA if prognosis poor - prevent further disease progression - rehabilitation decayed teeth ```
402
Outline steps in treatment planning for prevention in children
``` Pain relief Prevention - OH - appropriate fluoride - dietary control - FS - appropriate X-ray Desiree dentition ```
403
Discuss OH regimen in prevention of caries in children
``` Advise and encourage effective OH regime Advise/demonstrate brushing methods Emphasis of systematic brushing Supervised brushing <7 Spit not rinse ```
404
Discuss appropriate fluoride in prevention of caries in children
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
Discuss diet control and FS in prevention of caries in children
Diet - keep diet diary - 4d/24h - food, drink, snacks - advice on sugar freq./intake, substitutes FS; usually permanent molar, depends on risk
406
5 criteria for failed restoration
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
Discuss invasive caries into dentine as reason for failed restoration
Symptoms - usually none - discolouration ant. - pulpitis Signs marginally - visual; not approximally - radiography; approximally - tactile Signs deep tissue - visual; sometimes - radiography; sometimes
408
Discuss pulpal necrosis as reason for restoration failure
Symptoms; pulpitis Signs - loss of vitality on sensibility testing - +/- peri-radicular radiographic change
409
Discuss loss of function and progression to caries as reasons for restoration failure
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
Discuss unacceptable appearance as reason for restoration failure
``` Marginal staining (ant.) Discolouration of ant. material Contrast w/ normal darkening of tooth Gingival recession; darker roots Desire for white fillings ```
411
4 main reasons for failed restorations
Pt factors Operator factors Material factors Chance (trauma)
412
Discuss pt factors for failed restorations
``` Cariogenic factors unchanged - diet - plaque - saliva/xerostomia - poor OH Para-functional habits Appearance unacceptable ```
413
2 main areas where operator errors can cause failure of restoration
Errors in planning | Errors in execution
414
Discuss errors in planning for failure of restoration
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
Discuss errors in execution causing failure of restorations
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
Discuss material factors that can cause restoration to fail
Causes differ b/w materials - #; too shallow amalgam - corrosion, dissolution, chemical degradation - wear; composite - discolouration/staining Some have much greater longevity (amalgam)
417
Discuss auxiliary retention in amalgam restorations
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
Discuss ways to improve composite restorations
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
3 main topical fluoride applications
Professionally applied Rinsing solutions Toothpaste
420
Discuss professionally applied topical fluoride
Gel, solutions, varnishes Red. caries 20-40% Has to be controlled by professionals Protocol for usage followed precisely
421
Discuss topical fluoride rinsing solutions
0. 2% 4nights/wk 0. 05% daily (more suitable) Red. caries 16-50% NaF most widely used
422
Discuss toothpastes as topical fluoride delivery
Cleaning, polishing, fluoride delivery Abrasives, detergents, humectants, binding agent, preservative, active agents
423
Discuss active agents of toothpaste
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
Discuss pre-eruptive and post-eruptive effects of fluoride deposition
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
Discuss cariostatic mechanisms of fluoride
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
Discuss fluoride toxicity in relation to dentistry
Inc. incidence tooth mottling Abscess formation around root dec. development of root leading to high level of tooth mottling
427
Discuss fluorosis
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
Discuss fluoride poisoning
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
Discuss use and deficiency of dietary proteins
Source of AA; 30g/d Use - growth - maintain N2 balance - recovery illness/starvation - synthesise Ig Deficiency - kwashiorkor - marasmus - dec. Ig in saliva
430
Discuss function of dietary carbs and fats
Fats - energy - EFAs; synthesis of lipid molecules - req. for fat soluble vitamins - some EFAs req. for calcification Carbs; energy source
431
2 classes of vitamins
Water soluble; B, C | Lipid soluble; D A K E
432
Function and deficiency symptoms of vit B
Metabolic intermediaries Regulators of RBC development Deficiency - pallor of lips - cheilosis or red, shiny glossitis - megaloblastic anaemia (B12) - local inflammation - mucosa pale
433
Function and deficiency of vit C
Powerful antioxidant Deficiency - swelling, redness of interdental papillae - purplish inflammation and loss of epithelium - petechiae - dec. collagen synthesis (scurvy) - weakened PDL - gingivitis
434
Function and deficiency of vit 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
Function, deficiency and excess vit D
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
Function and deficiency of vit K
Essential for synthesis of clotting factors Deficiency: failure of blood to clot
437
Discuss functions and deficiencies of essential minerals
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
Discuss causes, symptoms and treatment of xerostomia
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
What is alginate?
Irreversible hydrocolloid, elastic impression material
440
Composition of typical alginate
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
Discuss the setting reaction of alginate
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
Changes in state of alginate when water is added
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
How does the alginate retarding agent suppress setting?
Na3PO4/Na2CO3 PO4/CO3 ions being used suppresses the reaction Req. agent to inc. working T, w/o would set in bowl
444
Discuss pH changes in the setting of alginates and the role of pH controllers
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
What is chromoclone?
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
Discuss advantages of alginates
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
Discuss disadvantages of alginates
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
Discuss the dispensing of alginates
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
Discuss disinfection if set alginate impressions
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
Discuss different types of alginates
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
What is agar?
Reversible hydrocolloid elastic impression material
452
Properties of agar
Solid (gel) @ RT Viscous liquid @ 60degrees Revert back to gel on cooling Gelling (setting) physical process
453
Composition of agar
``` 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
Discuss dispensing of agar
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
Dis/advantages of agar
``` 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
Define root caries
Caries at or apical to the CEJ that has undergone clinically apparent change
457
Discuss epidemiology of root caries
W/ age more root surface exposed to oral environment SA of exposed root inc, More susceptible to caries Problem among dentate older people
458
Discuss aetiology of root caries
Progressive, destructive carious process; complex, multifactorial disease Factors - root exposure - OH - diet - saliva - denture wearing - less F- - occlusion - cariogenic bacteria
459
Discuss cariogenic microorganisms in relation to root caries
``` S. mutans, sobrinus Actinomyces Lactobacillus Yeasts Prevotella ```
460
Discuss classification of root caries by pattern of mineralisation
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
Why can root caries not be classified by colour?
Little evidence showing correlation b/w colour and texture of lesion
462
Discuss clinical classification of root caries
Active - well defined, soft, yellowish/light brown, covered by visible plaque Slowly progressing - brownish black - leather Arrested - shiny, smooth, hard - no microbial deposits
463
Histological appearance of root caries
Demineralisation of cementum extending into dentine
464
Outline the non-invasive and invasive methods of root caries management
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
Discuss clinical problems w/ management of root caries
``` 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
Discuss the pharmaceutical methods of root caries management
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
Discuss invasive management of root caries and difficulties associated w/ it
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
Discuss the importance of early detection of carious lesions
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
Rational for restoring teeth
``` 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
Discuss cavity design for amalgam
``` Brittle; weak in thin sections Margin angles >70 Mechanical retention - undercuts - grooves - slots - pins ```
471
Discuss cavity design of composite
Aesthetic Micro-mechanical retention to acid-etched enamel Adhesion to dentine via bonding agents Weaker cf amalgam
472
Discuss cavity design for GIC
``` Tooth coloured inf. cf composite Adhesive to tissues Release F Weaker cf composite Ideal for cervical abrasion cavities Good replacement for dentine ```
473
Discuss cavity design for gold restorations
Malleable and ductile Strong; protect weak cusps Mechanical retention from cavity features and cement
474
Ideal properties of impression material
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
Discuss uses of elastomer impression materials
Due to strength and dimensional stability - produce accurate replica teeth and supporting tissue - construction of full/partial denture, crowns, bridges, inlays
476
Discuss the dispensing of impression materials
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
How does setting reaction of impression materials affect dimensional stability?
Addition: no byproduct thus no setting shrinkage Condensation: small molecule byproduct thus setting shrinkage
478
Discuss the viscosities of elastic impression materials
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
Why can’t light-bodied/wash impression material be used by itself?
As little filler doesn’t have strength; tear easily on removal Records fine details
480
Discuss impression technique for putty and wash
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
Discuss dis/advantages of putty and wash technique
Advantage; record fine detail Disadvantages - 1 stage; materials mixed simultaneously - 2 stage; takes longer for 2 impressions
482
Discuss impression technique for dual viscosity
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
Discuss components of condensation silicones
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
Discuss setting of poly(dimethyl siloxane)
Condensation silicone | Ethanol byproduct
485
Discuss advantages and disadvantages of poly(dimethyl siloxanes)
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
Discuss the components of polyvinyldimethylsiloxanes
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
Discuss dis/advantages of polyvinyldimethylsiloxane impression material
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
Discuss components of polyether impression materials
Base paste - polyether polymer (terminal ethylene-imine groups) - fillers - plasticisers - pigments - flavourings - triglycerides Catalyst - initiator; cationic starter sulphonium tetraborate salt - fillers - plasticisers - pigments
489
Function of fillers, plasticisers and triglycerides in polyether impression materials
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
Discuss the setting reaction of polyether impression materials
Cationic (addition) reaction via ring opening
491
Discuss dis/advantages of polyether impression materials
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
Discuss components of polysulphide impression materials
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
Describe the setting reaction of polysulphide impression materials
Base reacts w/ PdO2 via condensation reaction w/ H2O byproduct
494
Dis/advantages of polysulphide impression materials
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
Discuss non-elastic impression materials
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
Discuss which impression materials do not meet ideal properties
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
Reasons for making/uses of study casts
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
What is post-damming?
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
If wax has been added to a impression tray to modify it how do we insure frenum attachments are still recorded?
Making V shape in wax where labial and buccal frenulum attachments are
500
Discuss pt management when taking alginate impressions
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
Discuss technique for taking alginate impression
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
Define occlusion and articulation
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
Describe Centric Relation and Intercuspal Position
``` 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
Describe positions 3, 4, 5 on Posselt's diagram
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
Discuss r and h on Posselt's diagram
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
Discuss points II and III on Posselt's diagram
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
Define Bennett angle and Bennett movement
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
Compare ant. and post. guidance
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
Discuss mutually protected occlusions
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
Discuss balanced articulation
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
Discuss building rapport w/ child pt
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
Common c/o of child pt
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
Distinguish b/w reversible and irreversible pulpitis
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
Distinguish b/w low, med, high caries risk
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
Eruption dates of 1ry dentition
Begins 6/12 +/- 6/12 6-12/12: As, Bs 14/12: Ds 18/12: Cs 24/12: Es
516
Compare anaesthesia and analgesia
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
Define LA
Drug which reversibly prevents transmission of nerve impulse in region applied w/o affecting consciousness
518
Structure of LA
Lipophilic, aromatic portion Amide/Ester linkage Hydrophilic amine portion
519
2 types of LA
Amides | Esters
520
Compare amide and ester LA
``` 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
Mechanism of action of LA
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
Discuss factors affecting mechanism of LA
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
4 constituents of LA
LA agent Vasoconstrictor: Ad, felypressin Reducing agent: stabilise vasoconstrictor by preventing oxidation of Ad Isotonic solution: Ringer's solution
524
What are vasoconstrictors and why are they added to LA?
Additives that control blood flow by red. vessel diameter Reasons - red. local bleeding (local infiltration) - less systemic absorption (red. toxicity) - prolong duration
525
Contraindications for vasoconstrictors in LA
Ad: unstable angina, controlled arrhythmias - inc. cardiac output, inc. blood pressure, risk arrhythmia (red. plasma K) Felypressin: late stage pregnancy
526
Discuss 3 common LA agents
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
Equipment req. for LA
Cartridge Syringe Needle
528
Discuss LA cartridge
Cylinder (clear plastic/glass), plunger, cap Contents, conc., expiry, manufacturer, batch no. 2.2/1.8ml
529
Discuss LA syringe and needle
Syringe: accept cartridge ``` Needle - SS, beveled - short 25mm; Long 35mm - gauge (thickness) — 30: fine, infiltration — 27: thick, block ```
530
Discuss the safety syringe
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
Administration routes of LA
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
Compare duration of lidocaine and prilocaine
Lidocaine w/ Ad - pulpal 45-1h - soft tissue 3-5h Prilocaine w/ VC - pulpal 1h - soft tissue 2-3h
533
7 factors affecting duration of LA
``` Environmental pH Drug pKa T of diffusion from needle to nerve T of diffusion away from nerve Nerve morphology Conc. Lipid solubility ```
534
Steps to interpretation of X-ray
``` Good quality X-ray Good viewing conditions Systematic approach - decide if anatomy, artefact, pathology - describe area of interest ``` For pathology need differential diagnosis
535
Rating system for X-rays
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
Factors affecting reviewing of X-rays
Luminance Resolution Contrast ratio DICOM
537
Discuss normal anatomy of maxilla and mandible seen in X-rays
``` 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
Discuss radiographic classification of caries
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
Factors affecting appearance of caries on X-ray
``` B-L thickness Superimposed images of tissues X-ray not paralleled Incorrect exposure factors Cervical burnout Mach band ```
540
What are cervical burnout and Mach band?
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
9 factors must be mentioned when describing lesion from X-ray
``` 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
Most important CN in dentistry
CNV: trigeminal
543
Function of trigeminal
Sensory: face, sinuses, teeth Motor: muscles of facial expression
544
Branches of trigeminal
V1: ophthalmic V2: maxillary V3: mandibular
545
Branches of V2
Post., mid., ant. sup. alveolar Greater and lesser palatine Nasopalatine
546
Branches of V3
``` Inf. alveolar nerve Incisive Mental Lingual Mylohyoid Long buccal Auriculotemporal ```
547
Function of branches of V2
``` 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
Function of branches of V3
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
Differences in infiltration in maxilla and mandible
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
Discuss palatal infiltration
0. 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
Dis/advantages of infiltrations
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
Regional block dis/advantages
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
What is the pterygomandibular space? Boundaries of it
Anatomical landmark used for ideal positioning of IANB ``` Post.: parotid Lat.: ramus Medially + inf.: medial pterygoid Sup.: lat. pterygoid Ant.: buccinator ```
554
Preparation steps for infiltration
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
Discuss aspiration in relation to LA
Avoid intravascular injection Safety syringe self aspirating - -ve pressure draws blood into cartridge if in vessel Check cartridge before delivery
556
Steps to performing infiltration
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
What must be recorded in pt records after LA?
``` Type of LA Vasoconstrictor + conc. Vol Batch no. Injection; site, needle Pt reaction ```
558
4 ways to make LA as painless as possible
Appropriate topical Hold mucosa taut Slow entry Slow delivery
559
When would a IANB be used?
Alveolar bone too thick (mandible) Avoid area infection Wider area anaesthesia req. w/ 1 injection
560
Discuss anatomical landmarks for IANB
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
Technique for IANB
``` 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
Common errors when administering IANB
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
Which area is not anaesthetised in IANB?
B soft tissues premolar-molar region | Req. long buccal block
564
Discuss articaine infiltration
``` Used to avoid IANB Also called intraseptal/supracrestal Buccal infiltration 27 gauge, short needle 5mm below tip papilla, 3mm from gingival margin ```
565
Discuss long buccal block
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
Discuss mental nerve block
Deliver to mental foramen Inserted through reflected mucosa aiming for bone region b/w premolar apices 1.5ml
567
Discuss palatal blocks
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
Epidemiology of dental disease in children
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
Factors that can help decision making in child pt
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
Possible parental and child problems associated w/ treating child
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
Difference between cleaning, disinfection and sterilisation
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
Outline risk assessment for instruments and recommendation for each group
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
Outline decontamination facilities
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
Discuss pre-sterilisation cleaning
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
Discuss ultrasonic bath
``` Mental instruments only Only cleans instruments Typically 20-40 degrees, 3 mins Rinse, drain, dry Titanium and stainless steel separately Inspect w/ magnifier ```
576
Discuss thermal washer disinfector
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
Discuss sterilisers and sterilisation cycles
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
Discuss instruments that require special considerations for cleaning
Endodontic files - single use - reusable: 1 pt if tracked through decontamination Single use - steel burs - saliva ejector - matrix bands
579
How can LA complications be avoided?
Medical and drug history - previous problems w/ LA - systemic conditions - medications which may interact - anxious/nervous pt
580
Risk groups for LA complications
Elderly Children Medically compromised
581
General types of unwanted effects due to LA
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
General 4 causes of unwanted LA effects
1. Injecting inappropriate solution 2. Injecting too much solution 3. Injection into wrong site 4. Bad luck
583
Discuss allergy as LA complication
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
Drugs that may interact w/ LA
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
Discuss possible problems w/ injecting too much LA
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
Discuss why hepatic function is important in LA side effects
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
Main sites that can cause problems if LA injected into
Intravascular (arterial, venous) Intraneural Parotid gland
588
Discuss injecting intravascularly as problem of LA
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
Discuss injecting into parotid gland as problem of LA
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
Discuss problems w/ intraneural LA injection
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
Discuss possible problems that may be due to bad luck injecting LA
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
Strategies to red. LA complications
``` 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
Aims of X-ray quality assurance
Produce diagnostic radiography of high standards | Red. radiation dose to pt & staff
594
How can X-rays be assessed?
``` Image quality Pt dose & X-ray equipment Personnel & training Working procedures Audits: compare to gold standard ```
595
Discuss how image quality of Xray can be assessed
Subjective: problematic Contrast Not pixelated/blurry Subject in frame
596
Why is quality assurance of X-ray important?
Red. no. repeats Inc. efficiency Determine all sources of errors to allow correction Red. costs Keep dose as low as reasonably practicable
597
5 general types of errors that occur to X-ray
``` Preparation Positioning Exposure factors Processing Resolution ```
598
Discuss preparation & positioning errors of X-rays
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
Discuss exposure errors of X-rays
kV, mAS, T Cervical burnout Underexposed
600
What are line pairs per mm?
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)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions