Composite Resin

Question 1

What are the constituents of composite?

Answer 1

Filer particles (glass such as quartz or microfine silica)

Resin (Bis-GMA)

Photoinitiator (campherquinone)

Silane Coupling Agent

Low weight dimethacrylates (TEGDMA)

Question 2

What are 6 properties of composite resin?

Answer 2

Aesthetic
bonds to tooth
biocompatible
radiopaque
high strength
high hardness
low setting shrinkage if used in correct increments

Question 3

What are the filler particles in composite?

Answer 3

These are made of glass and can be microfine silica or quartz

Types of filler particles includeL
- microfine
- hybrid
- conventional

Question 4

What happens as we increase the filler content of composite?

Answer 4

Increased hardness and decreased thermal expansion

Question 5

What is the resin in composite?

Answer 5

Bis GMA that is a bifunctional molecule that allows carbon to carbon cross linking during polymerisation - it undergoes FRAP and composite hardens

Question 6

What is the photo initiator?

Answer 6

Campherquinone - creates free radicals when activated by blue light which initiate the free radical addition polymerisation

Question 7

What is the low weight dimethacrylates?

Answer 7

They alter material viscosity preventing it setting too fast

Question 8

What is the silane coupling agent?

Answer 8

This is in composite to bind the resin and the filler particles together (instead of glass binding to water)

Question 9

Describe how composite bonding works

Answer 9

Composite is a material that is composed of filler particles, resin (Bis-GMA), photo initiator, low weight dimethacrylates and a silane coupling agent

The composite is placed in the tooth and then blue light is used to activate the camperhquinone which produces free radicals which initiate a free radical addition polymerisation reaction within the resin (due to the carbon to carbon double bonds which crosslink forming larger molecule). the silane coupling agent bonds the resin and the filler together (instead of filler to water). The polymerisation reaction results in the hardening of composite

Question 10

What is hybrid composite?

Answer 10

Composite with mixture of conventional and microfine particles - increases hardness of composite, strength, improved aesthetics, reduced thermal expansion

Question 11

What is light cure?

Answer 11

This is where we use blue light to activate campherquinone (photoinitato) that produces free radicals that initiate free radical addition polymerisation

Question 12

What is problem with composite?

Answer 12

Can use too large increments resulting in inadequate depth of cure = unreacted monomer can leech and irrigate the pulp

Can use too large increments and bind walls together which can result in polymerisation shrinkage and then can lead to micro leakage and early failure

Question 13

What affects composite wear?

Answer 13

Finishing
Placement
Location
Cavity size and design
occlusion

Question 14

Why cant we leave caries at ACJ?

Answer 14

Will reult in unsupported enamel and can lead to early breakdown of restoration

Question 15

What size increments do we place?

Answer 15

2mm as this is depth of cure of composite

Question 16

What are the principles of cavity preparation?

Answer 16

1. identify and remove carious enamel
2. remove enamel to identify the maximal extent of caries at the ADJ
3. smooth enamel margins
4. circumferentially remove carious dentine
5. then remove deeper dentine carious over the pulp (consider liner later)
6. outline form modification - ensure no sharp angles
7. internal design modification

Question 17

What are some advantages of compoite?

Answer 17

Aesthetic
Bonds to the tooth
Command set
Conserves tooth tissue
low thermal conductivity

Question 18

What is the C factor?

Answer 18

Ratio of bonded to unbounded surface areas (if high then inc chance of bond failure)

Question 19

How is amalgam held in?

Answer 19

Retention and resistance form - need at least 2mm depth but less moisture sensitive