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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
What is the composition of zinc polycarboxylate?
Powder - zinc oxide, magnesium oxide Liquid - polyacrylic acid, copolymer
26
What are the strengths of zinc polycarboxylate?
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
What are the weaknesses of zinc polycarboxylate?
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
What are the indications of zinc polycarboxylate?
Metal supported restorations with mechanically retentive preps Poorly retentive provisional restorations
29
What is the composition of GIC?
Powder - silica, alumina, fluorides Liquid - polyacrylic acid, copolymers, tartaric acid, water
30
What are the strengths of GIC as a luting agent?
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
What are the weaknesses of GIC as a luting agent?
Slow setting initially Sensitive to eagerly moisture contamination Can cause pulpal sensitivity initially Low tensile strength and inadequate wear resistance Superseded by RMGIC
32
What are the indications of GIC as a luting agent?
Metal supported restorations with mechanically retentive preps Crowns with strengthened cores (where mechanically retentive) Where moisture control is adequate
33
What is the composition of RMGIC?
Powder - silica, alumina, fluorides, barium, ascorbic acid Liquid - HEMA, polyacrylic acid, tartaric acid, water, photoinitiators
34
What are the strengths of RMGIC as a luting cement?
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
What are the weaknesses of RMGIC?
Cement expansion can crack restorations Polymerisation shrinkage Excess needs removing quickly - excess difficult to remove Increased water absorption due to HEMA
36
What are the indications of RMGIC as a luting cement?
Metal supported restorations with mechanically retentive preps Crowns with strengthened cores (where mechanically retentive)
37
What are the advantages of cobalt chrome?
Stronger material Better tolerance and taste sensation More hygienic Better retention potential
38
What are the disadvantages of cobalt chrome?
Poorer aesthetics Difficult to add to, repair and adjust More expensive and involves more stages to make
39
What are the advantages of PMMA?
Excellent aesthetics Easier to add, repair and adjust Low density Cheaper to process and requires fewer stages to make
40
What are the disadvantages of PMMA?
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
When is greenstick used?
Border moulding and tray extension
42
When is impression compound used?
Complete dentures primary impressions
43
When is zinc-oxide used?
Master imps for complete dentures
44
Name the 4 components of alginate and their significance?
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
What are the advantages of alginate?
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
What are the disadvantages of alginate?
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
What happens if an alginate impression is left out in the open?
Syneresis - loss of moisture causing shrinkage leading to an inaccurate impression
48
What happens if an alginate impression is stored in wet conditions?
Imbibition - water absorbed by the gel, causing localised expansion of the imp where it has contacted water, leading to an inaccurate imp
49
What are the advantages of NaOCl as an irrigant?
Effective antimicrobial agent Excellent organic tissue solvent Lubricant Quick effective agent pH 11
50
What are the disadvantages of NaOCl as an irrigant?
Toxic Not substantive Ineffective in removing smear layer - why EDTA is recommended as penultimate irrigant
51
What are the properties of non-setting CaOH as an intracanal medicament?
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
What are the properties of ledermix as an intracanal medicament?
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
What are the advantages of GP?
Cheap Easy to handle Stable Doesn’t deteriorate Radiopaque Biocompatible Non-supportive of microbial growth Can be removed with heat or solvent
54
What are the disadvantages of GP?
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
What are the components of GP?
GP - 15% Zinc oxide - 65% Radiopacifier - 15% Plasticiser - 5%
56
What are the properties of root sealers?
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
Name 2 root canal sealers
Resin based - AH plus Zinc oxide/eugenol based - Tubliseal
58
What metals are found in amalgam?
Silver Tin Copper Zinc Mercury
59
What is creep?
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
Describe gamma, gamma-1 and gamma-2 amalgam
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
What is the copper content of copper enriched amalgam?
≥6%
62
What are the advantages of copper enriched amalgam?
Stronger at early stages and in longer term Less creep Higher corrosion resistance Less likely to fracture around margins
63
What is composite composed of?
Filler particles Resin Camphorquinone - photoinitiator Low weight dimethacrylates - allows control of mechanical properties Silane coupling agents - allows contact between filler and resin
64
What wavelength of blue light cures composite?
450nm

4 - misc (10 decks)

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