composite

Question 1

composition of comp

Answer 1

1 glass filler particles
2 resin
3 camphorquinon
4 low weight dimetharcylate
5 silane coupling agent

Question 2

sizes of filler particles

Answer 2

conventional 10-40um

fine

microfine extremely small about 0.04um

hybrid most common

Question 3

common resin

Answer 3

BIS GMA = bisphenol and glycidyl methacrylate

urethane dimethacrylate

Question 4

chemical structure of resins

Answer 4

c=c
difunctional molecules

Question 5

what sort of reaction does comp undergo

Answer 5

resin facilitate crosslinking when double bonds are activated by light

free radical addition polymerisation

Question 6

blue light wavelength

Answer 6

430-490nm

Question 7

do all resin monomers react?

Answer 7

only 30-80%

Question 8

what happens when resin is light cured and undergoes additon polymerisation

Answer 8

resin increases in molecular weight and viscosity and strength

Question 9

function of Low weight dimethacrylate

Answer 9

adjust viscosity and reactivity
adjust rate of polymerisation

Question 10

function of Silane coupling agent

Answer 10

allow intimate contact between filler and resin

normally water adheres to glass filler particle preventing resin from boding to surface

Question 11

is glass filler or resin stronger and harder

Answer 11

glass filler

Question 12

which filler type has the highest filler load

Answer 12

hybrid

Question 13

Effect of adding filler particles

Answer 13

o improved mechanical properties
o improves strength
o rigidity
o hardness
o abrasion resistance
o lower thermal expansion
o lower polymerisation shrinkage because less resin as a % of volume
o less exothermic
o improved aesthetics

Question 14

types of Curing method of comp

Answer 14

self cure 2 paste
light cure 1 paste

Question 15

posterior restoration use what type of filler particle comp

Answer 15

heavly filled

Question 16

anterior restoration use what type of filler particle comp

Answer 16

microfine or submicron hybrid

Question 17

Advantages of light curing

Answer 17

• extended working time
• short setting time
• higher filler levels than 2 paste
• less porosity than 2 paste
• less bubbles, voids which makes the material weaker

Question 18

Disadvantages of light curing

Answer 18

• premature polymerisation
• overly optimistic depth of cure
• retinal damage
• exothermic rxn might damage pulp and soft tissues
• polymerisation shrinkage -> debond -> microleakage
• If you use increments that is >2mm, soggy bottom, underpolymerised base, wont bond to underlying tooth fully

Question 19

recommended setting time

Answer 19

> 30s

Question 20

Differing definitions of DoC

Answer 20

Old ISO4049 definition:
Height of the residual fully cured composite divided by 2

New definition:
DoC is defined as the depth at which the material hardness is about 80%-90% that of the cured surface

Question 21

DoC definition

Answer 21

Which is defined as the layer thickness you can apply while ensuring the composite is cured adequately

Question 22

DoC values

Answer 22

• 2mm for hybrid comp
• up to 6mm for bulk fill comp but usually 4mm

Question 23

What is bulk fill?

Answer 23

• can place larger increments in bulk

Question 24

what light source for bulk

Answer 24

polywave

Question 25

what photo initiator in bulkfill

Answer 25

• Lucerin initiator + camphorquinone

Question 26

thermal properties of CR

Answer 26

• high thermal expansion (bad)
• low thermal diffusivity (good)
• low thermal conductivity (good)

Question 27

MECHANICAL properties of CR

Answer 27

• stronger than enamel and dentine
• hard
• rigid
• bonds to tooth

Question 28

does enamel or dentine have higher frature stress and rigidity

Answer 28

• enamel has higher fracture stress and rigidity ie more brittle

Question 29

PL vs EL

Answer 29

PL= beyond PL, stress and strain not linear

EL=when elastic limit stress is released, material will still return to the original dimension. beyond EL, permanent deformation

Question 30

Conventional vs microfine vs hybrid in terms of strength

Answer 30

hybrid > conventional > microfine (lower EL and YM)

Question 31

aesthetics

Answer 31

microfine (smooth) > hybrid > conventional (staining)

Question 32

which thermal property should ideally be the same as tooth structure

Answer 32

thermal expansion

Question 33

what about composite affets plaque retention?

Answer 33

surface ruhgness

Question 34

what determines the surface roughness of the composite

Answer 34

size of the particles.

larger particles ie conventional will have more roughness because more resin removed first

Question 35

higher filler load = less or more wear?

Answer 35

less wear

Question 36

what clinical factors affect the wear of composite

Answer 36

clinical factors:
size of cavity
location ie post or ante
technique of placement
cure time
occlusion

Question 37

How does comp bond to tooth?

Answer 37

• acid etch for enamel
• dentine bonding system for dentine

Question 38

Advantages of GOOD composite bonding

Answer 38

• reduces microleakage
• counteracts polymerisation shrinkage
• no need for undercuts like amalgam so less tooth structure removed
• stress transfer to bone and tooth
• good bond spreads load evenly

Question 39

what happens when there is a poor bond between comp and tooth?

Answer 39

• poor bond concentrates stress as certain points leading to fracture or failure

Question 40

How to decide between RMGIC, compomer, composite?

Answer 40

• RMGIC for high caries risk
• compomer for medium caries risk
• comp for low caries risk

Question 41

what initiates free radical additoin poly

Answer 41

camphorquinone

Question 42

material factors affecting wear of composite

Answer 42

material factors:
glass filler type, some glass harder
particle size distribution
filler loading ie % of volume filled by particles
resin formula
coupling agent strength