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BDS2 CLINICAL Dental Materials > Composite > Flashcards

Composite Flashcards

1
Q

What is the ideal properties of composite

A 
mechanical (strength, rigidity, hardness) 
bonding to tooth/compatible with bonding systems
thermal properties
aesthetics 
radiopaque 
handling/viscosity
anticariogenic
smooth surface finish/polishable 
low setting shrinkage 
biocompatible
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2
Q

what are the 2 key components of composite resin

A

glass filler particles

resin material

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3
Q

what is the key feature of the filler particles and resin

A

they are the opposite of each other

resin is soft while the filler is hard

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4
Q

what are the 5 components of composite

A 
filler particles 
resin
camphorquinone
low weight dimethacrylates
silane coupling agent
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5
Q

what are the filler particles

A

they are made of glass - they are what allow the composite resin to be hard

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6
Q

what are examples of glass filler particles

A
  • Microfine silica
  • Quartz
  • Borosilicate glass
  • Lithium aluminum silicate
  • Barium aluminum silicate
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7
Q

what is hybrid composite

A

most common
has a little bit of the larger particles and a little bit of the microfine particles
The small particles fill the spaces between the large ones

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8
Q

what does more filler mean for the material

A

it is harder

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9
Q

what is the monomers used for resin

A

BIS-GMA

urethane methacrylate

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10
Q

what is BIS-GMA

A

reaction product of bisphenol-A and glycidyl methacrylate

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11
Q

what are the key characteristics of the resin monomer

A

it is a difunctional molecule and it is essential for the crosslinking required for the polymerization as it has C=C and it undergoes free radical addition polymerization

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12
Q

what is camphorquinone

A

activated by blue light to produce free radical molecules
imitates free radical addition polymerization of BIS-GMA
changes the resin properties to make it stronger

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13
Q

is all the monomer reacted?

A

no the degree of conversion of resin is only 35-80%

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14
Q

what is the function of the low weight dimethacrylates

A

they are added to adjust viscosity and reactivity
It improves the material to adjust its properties as if you cure without it then it sets too quickly and does not give us enough working time.

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15
Q

what is an example of a low weight dimethacrylates

A

TEGDMA

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16
Q

what is a silane coupling agent

A

it allows a bond between the filler particle and resin

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17
Q

why do the filler particle and resin not bond without the silane coupling agent

A

Normally water will adhere to glass filler particles preventing resin from bonding to the glass surface.

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18
Q

what is an example of a silane

A

methacryloxypropyltrimemethoxysilane

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19
Q

how does methacryloxypropyltrimethoxysilane work (silane coupling agent)

A

the methoxy groups hydrolyse to hydroxy group by reacting with the absorbed water or -OH groups on the filler

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20
Q

what are the different uses of composite

A
  • It is often used where aesthetics is important
  • Class III, IV, & V permanent restorations
  • Class II – limited occlusal wear
  • Labial veneers
  • Inlays, onlays – indirect techniques
  • Cores
  • Modified forms as luting cements (some dual cured)
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21
Q

how is composite classified

A

filler type
curing method
area of use
handling

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22
Q

what type of composite is used for anterior teeth

A

microfilled or sub micron hybrid

23
Q

what type of composite is used for posterior teeth

A

heavy filled

24
Q

what type of composite is universal

A

sub micron hybrid

25
Q

how can composite be classified based on its handling

A

can be condensable
syringable
flowable

26
Q

what is condensable composite

A

‘amalgam feeling’ – it is more viscous and is used for packing the cavity in a similar way to amalgam. Has a greater porosity.

27
Q

what is syringable composite

A

good adaption, less porosities, easy to apply

28
Q

what is flowable composite

A

lower filler content, more shrinkage, difficult to apply, place for them with fibre ribbons.

29
Q

how can composite be classed on curing method

A

light cured

self cured

30
Q

what would happen if we stuck to only one size of filer particle

A

if we only used a large filler particle we would run out of space and we would not be able to fill up the volume but if we put more of the smaller ones then we can get more filler particles per unit volume than if we restricted ourselves to the larger one

31
Q

what are the advantages of adding more filler particles

A

• Improved mechanical properties
o Strength
o Hardness
o Rigidity
• Improved aesthetics – it is the glass that reflects the light and is what is responsible for the tooth like appearance
• Increased abrasion resistance – the filler particles make it less easy to break the surface of the composite surface
• Lower thermal expansion (still not perfect)
• Lower polymerization shrinkage (still a problem)
• Less heat of polymerization (but not negligible)
• Some radiopaque

32
Q

what are the different types of curing

A 
self curing (two pastes) 
UV activation (obsolete, one paste) 
light curing (blue light 440 nm, one paste)
33
Q

what is direct curing

A

cured in the mouth

34
Q

what is indirect curing/post curing

A

cured outside the mouth

35
Q

what happens in self curing

A

Consists of benzoyl peroxide + aromatic tertiary amine which react to create the free radicals and start the polymerization reaction

36
Q

what happens in light curing

A

Blue light source activates the camphorquinone to create free radicals which breaks the resin C=C and start the polymerization reaction

37
Q

how did the halogen light cure work

A

was a box which had an ordinary halogen white light and a filter which would only allow the blue light to pass through.

38
Q

what is the peak of the halogen LCU

A

500nm - out of the camphorquinone absorption range

39
Q

what is the peak of the LED LCU

A

460 nm

40
Q

what is the peak of the camphorquinone absorption

A

460 nm

41
Q

why is LED better than halogen

A

Ideally the light source should focus on the optimum wave light.
LED is efficient as there is an overlap but its peak is the same as camphorquinone but for the old style halogen LCU it’s peak is well beyond that of camphorquinone showing that it is not as efficient as the LED for curing the composite.

42
Q

what are the advantages of light curing systems

A
  • Extended working time as it is on demand set
  • Less finishing
  • Immediate finishing
  • Less waste
  • High filler levels (not mixing two pastes)
  • Less porosity (not mixing two pastes) – porosity is not a good thing as it is more vulnerable to fracture
43
Q

where is most of the blue light absorbed

A

close to the surface and this means that the composite resin nearest the surface sets the most readily and becomes hard as there is more polymerization at the surface and the molecules are harder and heavier

44
Q

what is sufficient polymerization

A

where the hardness of the material is half of that of the surface – this is typically around 2mm and this is why we use increments when building a restoration

45
Q

what does an increment greater than 2mm result in

A

underpolymerised base

leads to early failure

46
Q

what do bulk fill composites claim

A

cure depth of up to 6mm

47
Q

how do bulk fill composites claim to cure up to 6 mm

A

they have lucerin initiator as well as camphorquinone

48
Q

what is the optical absorption spectrum of lucerin

A

UV

means we need to use poly wave curing light technology

49
Q

what are the variables that mean that the lab tests are not representative of the clinical situation

A
  • Can curing light be positioned the same as in a lab test?
  • Can optical rod be placed adjacent to tooth/composite
  • Does all blue light illuminate material?
  • Will composite polymerize (cure) fully?
  • What impact does ‘stray’ blue light have on tissue
50
Q

what are the potential problems of light curing

A 
light/material mismatch 
premature polymerization from dental lights 
optimistic depth of cure values
recommended setting times too short
polymerisation shrinkage
51
Q

what are the safety issues of light curing for patients

A

when you polymerase the reaction is an exothermic one - potential pulp damage

divergent light beam

modern devices are brighter/more intense

illumination of patient’s soft tissue causing thermal trauma

52
Q

what is the temperature for potentially irreversible traumatization to the dental pulp

A

5.5 degrees

53
Q

what is the danger of light curing to clinical staff

A

ocular damage

BDS2 CLINICAL Dental Materials (15 decks)

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