DMS Summary

Question 1

What are the principles of cavity prep (6)

Answer 1

1. Identify and remove carious enamel
2. Identify max extent at ACJ
3. Remove peripheral caries then circumferentially deeper
4. Remove deeper caries over the pulp
5. Outline form modification
6. Internal design modification

Question 2

Name some advantages of composite (5)

Answer 2

• Aesthetics
• Bond to tooth
• Command set
• Conserves tooth tissue
• Low thermal conductivity

Question 3

What is the c factor

Answer 3

Ratio of bonded to unbonded SA

Question 4

List some properties of composite

Answer 4

Radiopaque
Low setting shrinkage
Low thermal conductivity
Bonds to tooth
Biocompatible
High strength

Question 5

What is composite composed of?

Answer 5

Filler - glass quartz

Resin - bis GMA

Photoinitiator - campherquinone

Low weight dimethacrylate - TEGDMA

Silane coupling agent

Question 6

Different types of filler particles (3)

Answer 6

Conventional
Hybrid
Microfine

Question 7

Function of resin bisgma

Answer 7

Undergoes free radical addition polymerisation

Difunctional molecule to allow c=c cross linking

Question 8

Function of initiator

Answer 8

Produces free radicals

Question 9

Function of silane coupling agent

Answer 9

Allows glass to bond to resin
Methoxy group reacts with absorbed water

Question 10

Clinical factors that affect wear of composite (5)

Answer 10

Placement
Curing
Finishing
Occlusion
Cavity size + design

Question 11

What is amalgam made of?

Answer 11

Liquid - mercury

Powder - copper, silver, tin, zinc

Question 12

What are the types of particles in amalgam?

Answer 12

Lathe cut
Spherical

Question 13

Setting reaction for amalgam

Answer 13

Powder + liquid –> unreacted particles + amalgam matrix

Question 14

Unreacted zinc potential issues

Answer 14

Reacts with saliva/blood

Forms zinc oxide + H bubbles = increased pressure expansion of AM

or

decreased pressure = pulpal pain

Question 15

List some properties of amalgam

Answer 15

High thermal conductivity
Corrosion
Longer handling
Not moisture sensitive
Cheaper
Worse aesthetics
Mercury toxicity
Mechanical retention required

Question 16

Constituents of GI (2)

Answer 16

Powder
- Silica
- Alumina

Liquid
-Polyacrylic acid
- Tartaric acid

Question 17

3 phases of the acid/base setting reaction for GI

Answer 17

1. Dissolution
2. Gelation
3. Hardening

Question 18

What happens at dissolution phase?

Answer 18

H ions diffuse into glass

Question 19

What happens at gelation phase?

Answer 19

Ca ions crosslink
Initial set of GI

Question 20

What happens at hardening phase?

Answer 20

Continued cross linking

Can last 7 days

Question 21

What can happen if there is contamination during setting?

Answer 21

Al ions diffuse out material
Water absorbed from saliva/blood

Question 22

Constituents of RMGI

Answer 22

Powder (barium glass)
Liquid (HEMA, tartaric acid, polyacreyic acid, photo initiator)

Question 23

Setting reaction for RMGI

Answer 23

Dual curing - acid base
Tri curing - redox

Question 24

Name 3 examples of liners

Answer 24

CaOH

ZOE

RMZOE

Question 25

How does CaOH work to protect pulp

Answer 25

Bacteriocidal (alkaline) Imitates odontoblast layer --> necrosis --> forms tertiary dentine to protect pulp

Question 26

When to not use ZOE

Answer 26

Do not use under composite Inhibits resin set

Question 27

List some properties of acrylic (denture base)

Answer 27

Dimensionally accurate High thermal conductivity Non toxic Non irritant Poor mechanical strength

Question 28

2 types of PMMA

Answer 28

Self cure - URA Decreased fracture resistance Light cure - Denture Increased fracture resistance

Question 29

List some ideal properties of a denture base (7)

Answer 29

Aesthetics Cost effective Non toxic/irritant Low weight Dimensionally stable High thermal conductivity Flexural strength

Question 30

Consistuents of PMMA (2)

Answer 30

Powder - PMMA, plasticiser Liquid - methacrylate, inhibitor

Question 31

Faults during production of PMMA (acrylic)

Answer 31

Contraction porosity Gaseous porosity Granular Crazing

Question 32

How do we bond to enamel?

Answer 32

Enamel = hydrophobic + high surface energy 37% phosphoric to roughen enamel + allow micro mechanical interlocking of resin fillers Improves wettability Removes contaminants

Question 33

How do we bond to dentine?

Answer 33

Dentine = hydrophilic + low surface energy Dentine conditioner - Etches dentine - Opens up dentinal tubules and removes smear layer Primer - HEMA/MDP, 4META = coupling agents - Bifunctional with hydrophobic + hydrophilic ends Adhesive - Mix of bisGMA+HEMA forms hybrid layer

Question 34

Give examples of non elastic impression materials

Answer 34

ZOE Impression compound

Question 35

Give examples of elastic impression materials

Answer 35

Hydrocolloid Alginate + agar Silicones Polyether

Question 36

Give examples of elastomer impression materials

Answer 36

Polyether + silicones

Question 37

Definition of an elastic impression material

Answer 37

Records undercuts Elastic strain + elastic recovery

Question 38

Definition of a non elastic impression material

Answer 38

Can't record undercuts is rigid

Question 39

Definition of mucostatic material

Answer 39

Fluid material that displaces soft tissues slightly and gives impression of undisplaced mucosa

Question 40

Definition of a mucocompressive material

Answer 40

Viscous material that records impression under load + takes impression of displaced tissues

Question 41

Ideal properties of an impression material

Answer 41

- Biocompatible - Non toxic/irritant - No thermal contraction - Operator convenient - 100% elastic recovery - Unaffected by moisture

Question 42

What type of material is alginate?

Answer 42

Elastic hyodrocolloid

Question 43

Constituents of alginate

Answer 43

Sodium alginate Silicate powder Calcium phosphate

Question 44

Advantages of alginate

Answer 44

Sets fast Cheap Adequate surface detail

Question 45

Disadvantages of alginate

Answer 45

Poor dimensional stability Distortion Operator dependent 3mm thickness required

Question 46

What type of material is impression compound?

Answer 46

Non elastic mucocompressive

Question 47

Advantages of impression compound

Answer 47

Mucocompressive Good for edentulous Can alter set

Question 48

Disadvatanges of impression compound

Answer 48

Mucocompressive - avoid in flabby ridge Rigid Poor dimensional stability

Question 49

What type of material is polyether?

Answer 49

Elastic elastomer - Impregum

Question 50

Advantages of polyether

Answer 50

Hydrophilic - good for poor moisture control Dimensionally stable

Question 51

Disadvantages of polyether

Answer 51

Rigid when set - not for undercuts Difficult to remove Absorbs water

Question 52

When are light + medium bodied silicones used?

Answer 52

Crowns bridges dentures

Question 53

Disadvantage of silicone

Answer 53

Hydrophobic