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4 - misc > stuff you use > Flashcards

stuff you use Flashcards

1
Q

What are the advantages of amalgam?

A

Durable - can withstand occlusal forces
Good mechanical properties
Less technique sensitive than resins and GIC
Low cost
Easy to manipulate and place
Good longevity

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2
Q

What are the disadvantages of amalgam?

A

Sensitive to mixing technique
Poor aesthetics
Doesn’t bond to enamel and dentine
Doesn’t release fluoride
Contains mercury - must be handled and disposed of correctly
Usually requires larger cavity preparations to provide mechanical retention
Experiences creep

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3
Q

When can amalgam not be used according to the minimata convention?

A

Patients under 15
Pregnant women
Breastfeeding women

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4
Q

What are the advantages of composite?

A

Polishable at placement
Command set
Good aesthetics
Conservation of tooth substance - cavity design driven by caries removal
No galvanic pain
No mercury
Bonds to enamel and dentine

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5
Q

What are the disadvantages of composite?

A

Adhesive system necessary
Technique sensitive
Requires excellent moisture control
Replacement will always increase cavity size
Post-op sensitivity
Polymerisation shrinkage
More expensive than amalgam

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6
Q

What are the advantages and disadvantages of total etch?

A

+ high strength bond to enamel
- removal of smear layer may increase post-op sensitivity
- technique sensitive
- risk of over-drying dentine - fibril collapse

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7
Q

What are the advantages of GIC as a restorative material?

A

Bulk placement
Sustained release of fluoride
Direct adhesion to enamel and dentine
Less technique sensitive than composite

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8
Q

What are the disadvantages of GIC as a restorative material?

A

Short working time
Long setting time - can take up to 24 hours to fully set
Moisture control still needs to be maintained - contamination with blood and saliva can reduce bond strength
Lack of translucency - poor aesthetics compared to composite

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9
Q

What can be done to improve bond strength of GIC?

A

Conditioning agent - 10% polyacrylic acid prior to placing

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10
Q

What are the different techniques for crown impressions?

A

Mono phase
Single-stage dual-phase
Two-stage dual-phase

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11
Q

What can be cemented with GIC?

A

PFM
Full metal crowns
Bridges

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12
Q

What can be cemented with RMGIC?

A

PFM
FMC’s
Bridges

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13
Q

What can be cemented with resin cements?

A

All-ceramic crowns
PFM
FMC’s
Bridges
Veneers

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14
Q

What are the different types of resin cements?

A

Light cured
Dual-cured
Self-cured

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15
Q

What can zinc phosphate be used to cement?

A

PFM
FMC’s
Bridges with retentive preps

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16
Q

What can zinc polycarboxylate be used to cement?

A

PFM
FMC’S
Bridges in low stress areas

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17
Q

How do you bond resin to ceramic?

A

Ceramic crown:
- pre-treat with silane
- sandblast
- etch with 5% hydrofluoric acid
Tooth:
- etch with 37% phosphoric acid
- apply dentine bonding agent

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18
Q

How do you bond resin to metal?

A

Base metal alloys - sandblast
Precious metal alloys - metal primer and sandblast
Tooth - etch with 37% phosphoric acid and dentine bonding agent

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19
Q

What are the different types of luting cements?

A

Zinc phosphate
Zinc polycarboxylate
GIC
RMGIC

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20
Q

What is zinc phosphate composed of?

A

Powder - zinc oxide, magnesium oxide, silicone dioxide, bismuth trioxide, calcium oxide, barium oxide
Liquid - phosphoric acid, water, buffering agents

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21
Q

What are the strengths of zinc phosphate?

A

Good compressive strength
Sufficient film thickness
Reasonable working time
Can be used in regions of high masticatory stress or long span prosthesis
Resistant to water dissolution

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22
Q

What are the weaknesses of zinc phosphate?

A

No adhesion to tooth
Requires mechanical retention
Dissolves in acids
Lacks antibacterial properties
Highly acidic (can cause pulpal sensitivity)
Low tensile strength

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23
Q

What are the indications of zinc phosphate?

A

Metal supported restorations with mechanically retentive preps

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24
Q

What are the contraindications of zinc phosphate?

A

Composite and all ceramic crowns due to lack of adhesion

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25
Q

What is the composition of zinc polycarboxylate?

A

Powder - zinc oxide, magnesium oxide
Liquid - polyacrylic acid, copolymer

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26
Q

What are the strengths of zinc polycarboxylate?

A

No adverse effect on the pulp
Bonds to enamel and dentine
Bonds to stainless steel
Fluoride release
Good compressive strength
Some resistance to water dissolution

27
Q

What are the weaknesses of zinc polycarboxylate?

A

Low adhesion and low tensile strength
Difficult to obtain in low film thickness
Dissolves in acids
Manipulation is critical
Film thickness may interfere with proper seating

28
Q

What are the indications of zinc polycarboxylate?

A

Metal supported restorations with mechanically retentive preps
Poorly retentive provisional restorations

29
Q

What is the composition of GIC?

A

Powder - silica, alumina, fluorides
Liquid - polyacrylic acid, copolymers, tartaric acid, water

30
Q

What are the strengths of GIC as a luting agent?

A

Fluoride release
Thermal expansion similar to tooth
Some resistance to acid dissolution
Adhesion to tooth and metal
Easy to use and effective when used properly

31
Q

What are the weaknesses of GIC as a luting agent?

A

Slow setting initially
Sensitive to eagerly moisture contamination
Can cause pulpal sensitivity initially
Low tensile strength and inadequate wear resistance
Superseded by RMGIC

32
Q

What are the indications of GIC as a luting agent?

A

Metal supported restorations with mechanically retentive preps
Crowns with strengthened cores (where mechanically retentive)
Where moisture control is adequate

33
Q

What is the composition of RMGIC?

A

Powder - silica, alumina, fluorides, barium, ascorbic acid
Liquid - HEMA, polyacrylic acid, tartaric acid, water, photoinitiators

34
Q

What are the strengths of RMGIC as a luting cement?

A

Superior compressive and tensile strength to GIC
Fluoride release
Less sensitive to early moisture control during setting
Easy to use
High bond strength to dentine
Adhesive to tooth and metal
Low film thickness
Decreased solubility

35
Q

What are the weaknesses of RMGIC?

A

Cement expansion can crack restorations
Polymerisation shrinkage
Excess needs removing quickly - excess difficult to remove
Increased water absorption due to HEMA

36
Q

What are the indications of RMGIC as a luting cement?

A

Metal supported restorations with mechanically retentive preps
Crowns with strengthened cores (where mechanically retentive)

37
Q

What are the advantages of cobalt chrome?

A

Stronger material
Better tolerance and taste sensation
More hygienic
Better retention potential

38
Q

What are the disadvantages of cobalt chrome?

A

Poorer aesthetics
Difficult to add to, repair and adjust
More expensive and involves more stages to make

39
Q

What are the advantages of PMMA?

A

Excellent aesthetics
Easier to add, repair and adjust
Low density
Cheaper to process and requires fewer stages to make

40
Q

What are the disadvantages of PMMA?

A

Brittle and susceptible to distortion
Low thermal conductivity
Less hygienic
Less strong compared to CoCr
Less tolerable for some patients
Needs to be bulkier for adequate strength

41
Q

When is greenstick used?

A

Border moulding and tray extension

42
Q

When is impression compound used?

A

Complete dentures primary impressions

43
Q

When is zinc-oxide used?

A

Master imps for complete dentures

44
Q

Name the 4 components of alginate and their significance?

A

Trisodium phosphate - controls setting time
Polysaccharide - allows for irreversible setting
Calcium salts - causes setting reaction by reacting with sodium
Filler - increases viscosity for better handling

45
Q

What are the advantages of alginate?

A

Non toxic, non irritant
Good surface detail
Ease of use and mix
Cheap
Good shelf life
Setting time can be controlled with temperature of water used

46
Q

What are the disadvantages of alginate?

A

Poor dimensional stability
Poor tear strength
Can distort if unsupported
Incompatible with some dental stones
Setting time dependent on operator handling
Messy and needs good mixing so no air bubbles

47
Q

What happens if an alginate impression is left out in the open?

A

Syneresis - loss of moisture causing shrinkage leading to an inaccurate impression

48
Q

What happens if an alginate impression is stored in wet conditions?

A

Imbibition - water absorbed by the gel, causing localised expansion of the imp where it has contacted water, leading to an inaccurate imp

49
Q

What are the advantages of NaOCl as an irrigant?

A

Effective antimicrobial agent
Excellent organic tissue solvent
Lubricant
Quick effective agent
pH 11

50
Q

What are the disadvantages of NaOCl as an irrigant?

A

Toxic
Not substantive
Ineffective in removing smear layer - why EDTA is recommended as penultimate irrigant

51
Q

What are the properties of non-setting CaOH as an intracanal medicament?

A

When RCT is to be done in 2 visits
High pH - 11 so bacteriocidal effect
Mild tissue irritant promotes apexogenesis (closure of root apex)

52
Q

What are the properties of ledermix as an intracanal medicament?

A

Steroid (triamcinalone) and antibiotic (chlortetracycline) paste
Used for dressing an inflamed vital pulp prior to commencing RCT
May use as intra-visit medicament if severe periradicular inflammation present

53
Q

What are the advantages of GP?

A

Cheap
Easy to handle
Stable
Doesn’t deteriorate
Radiopaque
Biocompatible
Non-supportive of microbial growth
Can be removed with heat or solvent

54
Q

What are the disadvantages of GP?

A

Lack of adhesion to dentine
Shrinkage on cooling when heated
When exposed to air and light it oxidises and becomes brittle - can be reconditioned with warm water

55
Q

What are the components of GP?

A

GP - 15%
Zinc oxide - 65%
Radiopacifier - 15%
Plasticiser - 5%

56
Q

What are the properties of root sealers?

A

Provide seal by good adhesion to canal wall
Flow into irregularities
Lubricante glide path of GP
Bacteriostatic
Encourage hard tissue repair
Set slowly to allow longer working time for GP compaction

57
Q

Name 2 root canal sealers

A

Resin based - AH plus
Zinc oxide/eugenol based - Tubliseal

58
Q

What metals are found in amalgam?

A

Silver
Tin
Copper
Zinc
Mercury

59
Q

What is creep?

A

When a material is subjected to a low level of stresses repeatedly over a long period of time resulting in flow which leads to permanent deformation

60
Q

Describe gamma, gamma-1 and gamma-2 amalgam

A

Gamma - good strength and corrosion resistance
Gamma-1 - good corrosion resistance
Gamma-2 - lacks strength and low corrosion resistance
1+2 make up amalgam matrix with gamma being unreacted particles

61
Q

What is the copper content of copper enriched amalgam?

A

≥6%

62
Q

What are the advantages of copper enriched amalgam?

A

Stronger at early stages and in longer term
Less creep
Higher corrosion resistance
Less likely to fracture around margins

63
Q

What is composite composed of?

A

Filler particles
Resin
Camphorquinone - photoinitiator
Low weight dimethacrylates - allows control of mechanical properties
Silane coupling agents - allows contact between filler and resin

64
Q

What wavelength of blue light cures composite?

A

450nm

4 - misc (10 decks)

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