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BDS2 DMS > Composite > Flashcards

Composite Flashcards

1
Q

name three advantageous properties of composite

A

aesthetic
strong
wear resistant

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2
Q

what three phases do composites exist as

A

resin matrix
dispersed inorganic filler particles
silane coupling agents

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3
Q

what size of composite filler particles are considered to be fine

A

0.5 -3 micrometres

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4
Q

what size of composite filler particles are considered to be microfine

A

0.04 micrometres - 0.2 micrometres

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5
Q

what size of composite particles are considered to be nanofilled

A

1-10 micrometres

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6
Q

name three clinical uses of composite

A

direct filling material for caries
abrasion/ erosion restoration
trauma

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7
Q

what are the five components of composite filling material

A

filler particles
resin
camphorquinone
low weight dimethacrylates
silane coupling agents

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8
Q

what is the purpose of camphorquinone

A

it is a photoinitiator

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9
Q

what is the function of low weight dimethacrylates in composite

A

allow mechanical properties to be varied

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10
Q

what is the function of silane coupling agents in composite

A

allows intimate contact between filler and resin

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11
Q

what monomers are used in the resin for composite material

A

Bis-GMA
urethane dimethacrylates

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12
Q

what is a key characteristic of a monomer for composite resins

A

has a difunctional molecule
- carbon-carbon double bonds that facilitate crosslinking that generate the growth of the monomer via free radical addition polymerisation

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13
Q

what does camphorquinone require to be activated

A

blue light

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14
Q

what does camphorquinone produce when activated by blue light

A

radical (electrically changed) molecules which initiate polymerisation of Bis-GMA

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15
Q

what are the two changes that occur to composite resin properties after activation of camphorquinone

A

increases molecular weight of resin
increases viscosity and strength

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16
Q

what is the action of silane coupling agents in composite

A

prevents moisture that might develop on the glass (filler) surface - which would prevent a good bond

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17
Q

where should microfilled or submicron hybrid composites be used

A

anteriorly

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18
Q

where should heavily filled composites be used

A

posterior

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19
Q

what type of composite resin can be used anywhere in the mouth

A

submicron filled

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20
Q

which type of composite material has the highest filler loading capacity which is wanted for a stronger material

A

hybrid composite resin

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21
Q

name four effects of adding more filler particles to composite

A

improved mechanical properties
lower thermal expansion
lower polymerisation shrinkage
improved aesthetics

22
Q

how does light-cure composite become activated

A

blue light (430-490 nm) activates camphorquinone which forms free radicals, breaking double bonds which establishes polymerisation reaction

23
Q

how do self cured composites become activated

A

when the 2 pastes are mixed together they produce free radicals, breaking double bonds and allowing polymerisation reaction

24
Q

name three advantages of using a light-cure composite

A

extended working times
less finishing and polishing
higher filler particles

25
Q

why do light cure composites have higher filler composition that self cure composites

A

self cure composite requires 2 pastes to be mixed and must be low enough viscosity to allow this to happen

26
Q

what is the standard way of testing a composite’s depth of cure

A

cure composite in a cylinder - scrape soft uncured composite from bottom, half the volume of hard composite that remains and this value is considered depth of cure

27
Q

what is the hardness profile of a composite

A

the depth of cure is the depth at which the hardness is 80% of the top surface

28
Q

which layer of thickness should you use for hybrid composites

A

2mm increments

29
Q

name three potential problems of light curing composite

A

premature polymerisation from dental lights
optimistic depth of cure values
light/ material mismatch leading to overexposure

30
Q

name four factors that depth of cure depends on

A

product
shade
duration of light exposure
intensity of blue light source

31
Q

name two patient considerations when using light cure composite

A

it is an exothermic reaction - can be damaging to the pulp if not sufficient hard tissue left
diverging blue light beam

32
Q

name two of the main concerns of polymerisation shrinkage

A

poor bonding to tooth/ microleakage
potential for cuspal fracture

33
Q

how does the fracture strength of composite resin compare to enamel

A

it is better than enamel (350 MPa for composite)

34
Q

what characteristics would a composite being placed in large posterior cavity require

A

high strength
high young’s modulus (rigidity)
high abrasion resistance

35
Q

what is one advantage and one disadvantage of conventional filler composite

A

strong
problems with finishing due to soft resins and hard particles

36
Q

name one advantage and one disadvantage of microfine filler composites

A

smooth surface for longer due to smaller particles
lower fracture strength and easily abraded

37
Q

what three factors of composite affect its wear resistance

A

filler particle size distribution
resin type
effectiveness of coupling agent

38
Q

what is used to etch enamel when preparing the tooth for composite application

A

37% phosphoric acid for 20 seconds

39
Q

what is the purpose of acid etch technique

A

removing the top layer of enamel, revealing a notched sub-structure

40
Q

what are the aims of bonding to tooth structure

A

reduce microleakage
counteract polymerisation shrinkage

41
Q

what two characteristics does composite fall short on when compared to enamel and dentine

A

hardness
elastic modulus

42
Q

what is composite’s thermal conductivity

A

low - good as it avoids pulpal damage

43
Q

which materials match enamel and dentine the best for thermal expansion

A

glass ionomer cements

44
Q

when may composite filling materials be considered not biocompatible

A

if they are not fully cured which can lead to unpolymerised resin leaking out

45
Q

what does caries left at the ADJ result in

A

unsupported enamel and early breakdown of the restoration margin

46
Q

what is the smear layer and how is it removed

A

layer of organic material which is produced whenever a highspeed or slow speed handpiece is used on dentine
this is removed by etch

47
Q

when finishing a composite restoration, what is used for gross reduction

A

diamonds, carbide finishing burs
finish disks
strips of alumina

48
Q

what is used for final finishing of composite

A

abrasive impregnated rubber rotary instruments
disks
rubber cup with polishing paste

49
Q

why is a smooth finish of composite desired

A

to prevent retention of plaque

50
Q

when might flowable composites be indicated

A

cervical erosion
abfraction

51
Q
A

BDS2 DMS (2 decks)

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