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BDS2 Dental Materials Sciences > Composite Resin 1+2 > Flashcards

Composite Resin 1+2 Flashcards

1
Q

when do you use direct filling materials?

A
  • new dental caries
  • abrasion/erosion
  • failed restoration/ secondary caries
  • trauma
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2
Q

ideal qualities of direct filling materials (11)

A

Mechanical – strength, rigidity, hardness
- Very important as need to be strong enough to withstand forces exerted on it

bonding to tooth / compatible with bonding systems

thermal properties

aesthetics

range of shades

radiopaque

handling / viscosity

anticariogenic
- glass ionomer cements

smooth surface finish/ polishable

low setting shrinkage

biocompatible

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3
Q

5 components of composite resin

A
  • filler particles
  • resin
  • camphorquinone
  • low weight dimerthacrylates
  • silane coupling agents
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4
Q

what are filler particles?

A

Glass

Lots of variety
–	microfine silica
–	quartz
–	borosilicate glass
–	lithium aluminium silicate
–	barium aluminium silicate
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5
Q

% volume of filler particles in conventional composite

A

50%

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6
Q

% volume of filler particles in microfine (submicron) composite

A

25%

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7
Q

% volume of filler particles in fine composite

A

60-70%

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8
Q

% volume of filler particles in hybrid composite

A

70%

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9
Q

filler particle size in conventional composite

A

10-40um

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10
Q

filler particle size in microfine (submicron) composite

A

0.04-0.2um

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11
Q

filler particle size in fine composite

A

0.5-3um

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12
Q

filler particle size in hybrid composite

A

range

0.01-0.1um and 1-10um

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13
Q

greater % volume of filler particles means….

A

the harder the material

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14
Q

what composite resin is most commonly used in GDH?

A

hybrid composite resin

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15
Q

what is the monomer in resin?

A

BIS-GMA
- reaction product of bisphenol-A and glycidyl methacrylate

urethane dimethacrylates

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16
Q

what is a key characteristic of the monomer in resin of composite resin?

A

difunctional molecule

C=C bonds – facilitate crosslinking

  • undergoes free radical addition polymerization
  • Needed to take composite resin to hard rigid on curing
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17
Q

what activates 3. Camphorquinone?

A

blue light

photo initiator
- initiates free radical addition polymerisation of BIS-GMA

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18
Q

what increases viscosity in composite resin?

A

cross linking of BIS-GMA with other molecules due to photo-initiation

no all monomers react

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19
Q

what is the purpose of low weight dimethacrylates in composite resin?

A
  • improve the material
  • added to adjust viscosity & reactivity

Without can set too quickly - allow time to place and pack
- Slow down so more control

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20
Q

what is the purpose of silane coupling agent in composite resin?

A
  • good bond between filler particle and resin is essential

normally water will adhere to glass filler particles, preventing resin from bonding to the glass surface
- a coupling agent is used to preferentially bond to glass and also bond to resin
intimate interface between the 2
- essential

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21
Q

uses of composites

A
  • where aesthetics important
  • Class III, IV & V permanent restorations
  • Class II - limited occlusal wear
  • labial veneers
  • inlays, onlays - indirect technique
  • cores
  • modified forms as luting cements (some dual cured)
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22
Q

4 ways to classify composite

A
  • filler type
  • curing method (light or self)
  • area of use (anterior, posterior or universal)
  • handling characteristics
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23
Q

what type of composites can be used in an anterior location?

A

microfine (submicron)

hybrid

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24
Q

what type of composites can be used in posterior location?

A

heavily % filled - hybrid

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25
Q

what type of composites can be used in universal location?

A

submicron

hybrid

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26
Q

what are the 3 types of handling characteristics of composite resin?

A

condesable

syringeable

flowable

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27
Q

what is condensable composite like?

A

amalgam feeling

greater porosity

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28
Q

what is syringeable composite like?

A

good adaptation
less porosities
easy to apply

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29
Q

what is flowable composite like?

A

lower filler content
more shrinkage
difficult to apply
place for them - fibre ribbons

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30
Q

why do you want more filler particles per unit volume?

A

get a stronger, harder, more rigid composite resin

use a variety of filler particle sizes to get in between larger ones

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31
Q

10 effects of adding filler particles

A
  • improved mechanical properties (strength, hardness, rigidity etc.)
  • improved aesthetics
  • glass reflects the light
  • gives more of a tooth like appearance
  • increased abrasion resistance
  • less easy to scrape surface, make divots
  • lower thermal expansion (still not perfect)
  • lower polymerisation shrinkage (still a problem)
  • less heat of polymerisation (BUT not negligible)
  • some radiopaque
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32
Q

3 classes of composite curing

A
  • self curing (two pastes)
  • UV activation (obsolete, one paste)
  • Light curing (blue light 440nm, one paste) Used most in GDH
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33
Q

2 different light sources for light curing composite resin

A

halogen - less efficient

LED

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34
Q

where is Camphorquinone peak absorption?

A

between 400 and 500nm

so ideally light cure is 450nm

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35
Q

6 advantages of light cure composite resin

A
  • extended working time i.e. on-demand set
  • less finishing
  • immediate finishing
  • less waste
  • higher filler levels (not mixing two pastes)
  • less porosity (not mixing two pastes)

self cure has more voids/gaps so increased porosity
Light cured - smooth and uniform
Porosity is bad makes material more vulnerable to fracture

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36
Q

why is porosity bad in composite resin?

A

makes composite resin more prone to fracture due to increased voids/gaps

37
Q

depth of cure

A

the depth to which the composite resin polymerises sufficiently,
- such that its hardness is about half that of the cured surface

38
Q

what is the typical depth of cure of composite resin?

A

2mm

39
Q

what will happen if increments are larger than 2mm?

A

under-polymerised base

‘soggy-bottom’
poor bonding to tooth -> early fracture

40
Q

5 potential problems with light curing composite resins

A
  • light / material mismatch – overexpose
  • premature polymerisation from dental lights - avoid exposure
  • optimistic” depth of cure” values
  • recommended setting times too short
  • polymerisation shrinkage - affects bond to tooth, potential for cuspal fracture, microleakage
41
Q

factors that can cause issue for light cure composite - light/cure mismatch

A

don’t match the composite resin absorption spectrum - check right wavelength for your material

42
Q

factors that can cause issue for light cure composite - premature polymerisation from dental lights

A

Background light contains blue light - can start to cause polymerisation so put cap back on material when not in use

43
Q

factors that can cause issue for light cure composite as optimistic depth of cure values

A

product, shade, light exposure & intensity

use small increments - 2mm max

44
Q

factors that can cause issue for light cure composite as recommended setting times are too short

A

product, light used, light/ material distance, contamination or damage to light guide, timer accuracy, variations in light output (e.g. over repeated use, between different units)

use > 30 s (more than suggested)

Inadvertently not aiming as should
- Recommend times can be less than desired due to inaccuracies in person

45
Q

factors that can cause issue for light cure composite due to polyermisation shrinkage

A

Bonding between composite resin and tooth itself fails
- Ensure uniform behaviour

  • use small increments - light from different angles
46
Q

light curing safety points for patient

A
  • Exothermic reaction
    (Release of heat in resin material; heat conducts to adjacent enamel/dentine)

Divergent light beam and Modern devices brighter/more intense
- idea is more intensity accelerates curing, reducing exposure duration needed
BUT unless optical rod is ALWAYS close to the composite resin surface SOME blue light MAY illuminate patient’s soft tissues
- Beam passes through a transformed optical rod
- Diverges. Can hit soft tissues
causing Thermal trauma/ injury to patient

47
Q

light curing safety for clinical staff

A

ocular damage

- use safety shields and/or safety glasses

48
Q

what is the fracture stress for composite resin?

A

350MPa

- strong

49
Q

what is the Elastic Young’s modulus for composite resin?

A

15GPA (15000MPA)

  • high
  • rigid
50
Q

how does the properties of composite resin meet it’s clinical requirements?

A

Large Posterior Cavity needs High strength, high YM, high abrasion resistance

Deciduous (large pulp) needs to be strong in thin section

wear = wear of tooth (not amalgam)
- other properties more important - bonding, microleakage

51
Q

characteristic properties of conventional composite resin

A

strong but problems with finishing and staining due to soft resins and hard particles

had large filler particles mean low quantity per volume poor finishing more likely to stain

52
Q

characteristic properties of microfine composite resin

A

smaller particles - smoother surface better aesthetics for longer period

but inferior mechanical properties (Elastic limit & Young’s Modulus)

53
Q

characteristic properties of hybrid composite resin

A

originally compromise between conventional & microfine

most modern composites are hybrids

improved filler loading and coupling agents have led to improvement in mechanical properties

54
Q

what is hardness?

A

refers to material surface

  • resistance to scratching
  • indentation resistance

cannot be derived from stress strain curve
• not stress

55
Q

hardness test

A

Indenter or made of stainless steel, has tapered point at end. Weight on top of indenter and leave on composite resin for set time.

Hard material = small indentation
- need a high powered microscope to measure

56
Q

abrasion

A

removal of surface layers when two surfaces make frictional contact
- Tooth grinds/slides along the opposing tooth surface (or restorative material at its surface).

happens if material is not hard

57
Q

what does abrasion effect?

A

increased surface roughness

  • not as attractive potential (notices by patient)
  • increased plaque retention
  • sensation when in contact with tongue (unpleasant)
58
Q

what is lost first from composite resin when it is worn?

A

loss of resin first and then filler particles as wear continues

degree of roughness felt depends on size of filler particles

59
Q

5 material factors affecting wear of composite resin

A
  • filler material
  • particle size distribution
  • filler loading (% present)
  • resin formulation (if resin is soft will abrade easily, relatively hard will resist abrasion more)
  • coupling agent (bonding filer particle to resin)
60
Q

6 clinical factors affecting wear of composite resin

A
  • cavity size & design
  • tooth position
  • occlusion
  • placement technique
  • cure efficiency (if you don’t cure composite resin effectively will not form expected properties. Not as hard so wear quicker)
  • finishing methods
61
Q

how does enamel bond to composite resin?

A

acid-etch technique

62
Q

how does dentine bond to composite resin?

A

dentine/universal bonding systems

63
Q

summary of acid etch technique on enamel

A
  • 30 % Phosphoric acid
  • 20 secs

fill with unfilled resin (no filler particles)
then follow with composite resin on top

64
Q

enamel to composite resin typical bond strength

A

40MPa

65
Q

dentine to composite resin typical bond strength

A

40MPa

66
Q

what causes micro-leakage?

A

gaps forming around composite

67
Q

what is polymerisation shrinkage?

A

material placed pulls away from tooth surfaces it has been bonded to
- good bond will reduce this chance

68
Q

composite resin cavity design

A

minimal (less tissue removal)

bond holds restoration in place

69
Q

importance of good bond strength of composite to tooth in terms of stress transfer

A

forces acting on base are spread evenly and equally and good bond then restoration likely to last

70
Q

what is stress transfer like when there is poor bond strength between composite and tooth?

A

poor bond and gaps/voids between composite resin and tooth tissue then stress force is not spread evenly as focuses on the voids.

Stress in these regions is great so more vulnerable to fracture
- restoration does not have to withstand full stress - stress transferred to tooth and bone

71
Q

is hybrid composite or micro-filled composite more resistant to abrasion?

A

hybrid

higher compressive strength 
higher elastic limit stress
higher tensile strength 
higher flexural strength 
double elastic modulus
triple hardness
72
Q

which has higher rigidity amalgam or composite resin?

A

amalgam - double Elastic modulus

73
Q

thermal conductivity of composite resin is….

A

low

74
Q

why is it advantageous that the thermal conductivity of composite resin is low?

A

avoids pulpal damage from hot and cold foods/fluids

- composite resin acts as insulator not a conductor

75
Q

the thermal expansion coefficient of composite resin is….

A

high compared to enamel, dentine and amalgam

glass ionomer cement is closest to tooth tissue range

76
Q

why is it disadvantageous that the thermal expansion coefficient of composite resin is high?

A

should be equal to the tooth to reduce microleakage

  • want to expand and contract at same rate as natural tooth tissue
  • this reduces void formation and microleakage
77
Q

what is the advantage of some composite resins being radiopaque?

A

can be seen in X-rays

  • see if any has fallen or been misplaced
  • diagnose secondary caries easily

e.g. Clearfill Majesty ES-2 used in clinical skills

78
Q

5 composite resins aesthetics positives

A
  • shade range
  • translucency
  • maintenance of properties over lifetime
  • resistance to staining
  • surface finish
79
Q

what does light curing give?

A

on demand setting

means can have mixing and working times adjusted to you

80
Q

is there variation in composite resin viscosities?

A

yes
pick one that is suited to your working preferences and cavity
- some flow and some need packed

81
Q

what is one of the most critical factors for patients?

A

aesthtics

so composite resins have a smooth polishable surface finish is good
- but technique sensitive can crystalise

82
Q

what helps minimise the impact of setting shrinkage in composite resin?

A

bonding agents and clinical techniques (carefully places increments)

83
Q

what happens to the non-polymerised monomers in the resin?

A

20% of monomers are captured in mass of composite resin

over time can be released
- irritates the surrounding tissue

84
Q

10 properties that impact choice of material

A
  • Mechanical
  • Bonding
  • Thermal
  • Aesthetic
  • Handling
  • Surface finish
  • Polymerisation shrinkage***
  • Anticariogenic
  • Biocompatible
  • Radiopacity
85
Q

what can polymerisation shrinkage lead to?

A

gaps/voids between restorative material and tooth

lead to micro-leakage and restoration failure

86
Q

when is resin modified glass ionomer most likely to be used in clinical setting?

A

with high caries risk patients

frequent dental attenders

87
Q

when is compomer most likely to be used in clinical setting?

A

with medium caries risk patients
caries is under control
regular dental attenders

88
Q

when is composite resin most likely to be used in clinical setting?

A

low caries risk patients

BDS2 Dental Materials Sciences (13 decks)

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