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Operative 2 > Biomaterials Review: Composite Resin: week 2 > Flashcards

Biomaterials Review: Composite Resin: week 2 Flashcards

1
Q

Polymethylmethacrylate (PMMA), 1940’s
(4)

A

◦ Unfilled resin
- MMA resin mixed with PMMA polymer beads
◦ High polymerization shrinkage (7%),
◦ High thermal expansion (90 ppm/C)
- Marginal leakage
◦ Low strength

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2
Q

Composite Definition:

A

a physical mixture of 2 or more materials with
superior properties as compared to the individual components.

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3
Q

Composite examples
(4)

A

◦ Concrete: cement + gravel
◦ Fiberglass
◦ Dentin: collagen matrix + hydroxyapatite crystals
◦ Dental composites: Resin + Filler Particles

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4
Q

Dental Composite Uses
(5)

A

Tooth-colored restorative material
Bonding agents (filler may be present)
Sealants (filled)
Composite resin luting agents (cement)
Resin-modified glass ionomer material

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5
Q

Resin matrix phase reinforced by

A

dispersed filler particle phase bound to
the resin by a silane coupling agent

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6
Q

Resin matrix

A

◦ Bis-GMA, TEGDMA

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7
Q

Filler particles
(2)

A

◦ Quartz
◦ Colloidal silica

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8
Q

Activator-Initiator system
(2)

A

◦ Usually photoinitiator is what we use
◦ Camphorquinone (sensitive to 470 nm visible
light) (Yearn, 1985)

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9
Q

Dental Composite Components
(6)

A

◦ Resin matrix
◦ Filler particles
◦ Coupling agent
◦ Activator-Initiator system
◦ Polymerization inhibitors
◦ Optical modifiers

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10
Q

Bis-GMA:

A

bisphenol A diglycidyl methacrylate
◦ Matrix in most North American products

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11
Q

TEGDMA: triethyleneglycol dimethacrylate
(4)

A

◦ ~30% added to Bis-GMA or UDMA
◦ diluting agent/viscosity controller
- used to dilute the BisGMA (or UDMA), which is very viscous
◦ Too much TEGDMA will increase the amount of polymerization shrinkage
◦ Helps to promote extensive cross linking
- results in a matrix that is more resistant to degradation by solvents.
- TEGDMA is another difunctional monomer (has two reactive ends)

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12
Q

*UDMA:

A

urethane dimethacrylate

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13
Q

Methyl methacrylate:

A

Monofunctional, only 1
reactive end

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14
Q

Adding filler particles — strength

A

INCREASES

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15
Q

Adding filler particles — polymerization shrinkage

A

DECREASES

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16
Q

Basics of Fillers:
(3)

A

◦ The more filler, the better
◦ Composite resin should have at least 75% filler by weight
◦ The smaller the size of the filler, the better

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17
Q

Crystalline silica (quartz),
types (2)

A

Crystalline silica (quartz),
◦ Ba, Li, Al silicate glass
◦ Amorphous silica

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18
Q

Filler Particles
◦ Dispersed in

A

resin matrix

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19
Q

Filler Particles
Distribution varies depending on the material
(3)

A

◦ filler loading %, expressed by weight or by volume
◦ filler size
◦ filler

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20
Q

Filler Loading Fraction
Dental composites:
— wt% or
— vol%

A

50-85
30-70

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21
Q

Benefits of Filler Particles
(6)

A

1.Reinforcement of resin matrix:
◦ Increase hardness, strength, elastic modulus, and wear resistance
2.DECREASED polymerization shrinkage: ~10% to ~2%
3.DECREASED thermal expansion and contraction
1.Fillers don’t expand or contract
4.Improved workability, handling
5.DECREASED water sorption
6.INCREASED radiopacity (Barium, Strontium, Zirconium)

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22
Q

Filler Size Distribution
Good distribution necessary to

A

incorporate maximum amount of filler

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23
Q

Silane
(4)

A

◦ Couples filler to resin matrix
◦ Allows stress transfer from flexible matrix to higher modulus
(aka less flexible) filler particle
◦Improves the mechanical properties
◦ Decreased water sorption along filler-resin interface

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24
Q

Resin polymerization (free radical
addition reaction)
(4)

A

◦ Activation: Activator converts
initiator into a free radical
◦ Initiation: Free radical initiator
starts the addition reaction
◦ Propagation: continued polymer
chain growth
◦ Termination

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25
Q

Polymerization Inhibitor
(4)

A

Prevent spontaneous polymerization when dispensed
Stop polymerization from brief room light exposure (reacts with free
radicals)
Once the blue light is used, all inhibitor quickly consumed=
polymerization chain reaction starts.
Butylated hydroxytoluene (BHT)

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26
Q

Butylated hydroxytoluene (BHT)

A

◦ Food preservative, reduce oxidation

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27
Q

Optical Modifiers
Pigments:

A

metal oxides

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28
Q

Optical Modifiers
Opacifiers:
(4)

A

◦ Titanium and aluminum oxide
◦ Control opacity or translucency
◦ Brand differences
◦ Dentin vs enamel composite shades

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29
Q

Different ways to classify composites based on:
(3)

A

• Filler particle size and size distribution
• Handling characteristics
• Type of polymerization

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30
Q

Classification by Filler Size and Distribution
(4)

A
  1. Macrofill
  2. Midifill
  3. Microfill
  4. Hybrids
    a. Midi-Micro Hybrid (Midi- or Microhybrid)
    b. Mini-Micro Hybrid (Microhybrid)
    c. Mini-Nano Hybrid (Nanohybrid)
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31
Q

Macrofill & Midifill Composites

A

NOT USED MUCH TODAY
10-100 m (macro)
1-10 m (midi)
65-70 wt%
Large fillers
◦ Rough surface finish
Not good size distribution
◦ Increased inter-filler resin space, low wear resistance
Prone to staining
Brands: Adaptic (macro)
Concise (midi), still on market

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32
Q

Microfill Composite

A

0.01-0.1 m particles, colloidal silica
40-60 wt%
◦ Due to large filler surface area, difficult to increase filler fraction, too viscous
Excellent finish, Best wear resistance of this generation
Weakest
Use for esthetic, low-stress sites
◦ Class III
◦ Layer over hybrid, kit systems
Brands: Durafill VS, Epic TMPT, Renamel, Heliomolar

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33
Q

Hybrid Composites

A

Midi-Micro Hybrid (First hybrids)
◦ Typically called Microhybrids
◦ Mix of midi and microfillers,
1-10 & 0.01-0.1 m
◦ 75-80 wt%
◦ Improved surface finish
compared to macro and midi composites
◦ High strength
◦ Many of the of current materials are hybrid
◦ Z250, Z100, Herculite, TPH, APH, Point 4

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34
Q

Mini-Micro Hybrid

A

a. Also called Microhybrids
b. Mix of mini and microfillers,
0.1-1 and 0.01-0.1 m
c. 80-85 wt%
d. Newer material
1) Smoother finish than midi-micro hybrid
2) Slightly lower strength
e.Clearfil APX, 4-Seasons, Miris, Vitalescence, Synergy, Tetric, EsthetX

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35
Q

Mini-Nano Hybrid (Nanohybrid)

A

◦ Nanometer: 10-9 Micrometer: 10-6
◦ Mix of mini, and nanofillers,
0.1-1 and 0.001-0.01 m (1-10 nm)
◦ ~80 wt%
◦ Newest materials: Filtek Supreme Ultra (what is used in clinic), Premise,
TPH3 (what you use in lab), Simile
◦ Strength comparable to microhybrids and finish
equivalent to microfills
◦ Not all “nanocomposites” contain nanofiller (<100
nm), filler size reported in nm,
i.e. 300 nm

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36
Q

Classification by Handling Characteristics (3)

A

Regular
Flowable
Bulk Fill

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37
Q

Flowable Composite
(3)

A

Low viscosity hybrid
Reduced filler,
40-60 wt%, adapts better without handling

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38
Q

40-60 wt%, adapts better without handling
(4)

A

◦ Lower filler percentage, decreased modulus, increased flexibility
◦ May be used under regular composite at gingival floor of Class II
◦ Thought may compensate for polymerization shrinkage stress and reduce gap
formation at gingival floor.
◦ However, research does not support theory.

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39
Q

Many are not radiopaque
◦ Big problem=

A

difficult to distinguish from recurrent caries

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40
Q

Flowable
shrinkage vs stress

A

◦ more shrinkage
◦ lower filled
◦ less stress
◦ has more resin to relieve the stress as it cures
◦ good in abraction areas

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41
Q

Hybrid
shrinkage vs stress

A

◦ less shrinkage
◦ higher filled
◦ more stress

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42
Q

Bulk fill

A

Newer technology- to avoid incremental placement
◦ One “bulk” placement
Need high output lights, at least 20 seconds
◦ ~ 1000 Mw/cm2
◦
Needed to cure through larger increments of material (up to 4-5mm)
Highly filled
◦ more translucent fillers
◦ which do not shrink
◦ = less resin matrix
◦ which does shrink
◦ Higher filled = more stress
◦ less resin to relieve the stress when it cures

43
Q

Bulk fill
Classified by type:
(2)

A

Flowable BASE Bulk-fill
Full-body Bulk-fill
◦ Need more evidence to promote this use

44
Q

Packable

A

Mini and midi fillers, >80 wt%
Supposed to handle like amalgam
◦ Marketed as amalgam alternatives
◦ Called “condensable,” but this is inaccurate
Conventional hybrids have superior properties
Bulk cure inadequate
P60, Surefil, Alert
Not well-accepted

45
Q

Classification by Polymerization Activation
(3)

A
  1. Self-cure, chemical activator
  2. Light-cure, blue light activator
  3. Dual-cure, combination of both
46
Q

Chemical or Self-cure Composite

A

2-paste system, 1 with activator, 1 with initiator
◦ Mixed to begin polymerization

47
Q

Chemical or Self-cure Composite
Activator:
Initiator:

A

Aromatic tertiary amine
Benzoyl peroxide (BPO)

48
Q

Chemical or Self-cure Composite
Advantage:

A

bulk placement

49
Q

Chemical or Self-cure Composite
Disadvantages
(3)

A

◦ Mixing, incorporate bubbles, decrease strength
◦ No control of working time
◦ Amine, not color stable

50
Q

Light-cure Composite

A

One-paste system

51
Q

Light-cure Composite
Activator:

A

Blue light (~470 nm)

52
Q

Light-cure Composite
Initiator:
(2)

A

◦ Camphorquinone (CQ), photoinitiator
◦ DMAEMA, alphiatic amine (accelerator)

53
Q

Light-cure Composite
Advantages
(3)

A

a. Mixing not required, less porosity, increased
strength
b. Aliphatic amine (DMAEMA) more color stable
than self-cure aromatic tertiary amine
c. Better control of working time

54
Q

Light-cure Composite
Disadvantages
(2)

A

a. Limited light penetration, ≤ 2mm increments, 20
sec
b. Blue light, retina damage – use orange shield

55
Q

Light-cure Composite
Curing equipment factors:
(3)

A

◦ Bulb output, ≥ 300-400 mW/cm2
(11mm tip)
- At least 550 mW/cm2 for TPH3 or Filtek Supreme
- At least 1000 mW/cm2
for Bulk Fill
◦ Fiber-optic bundle breakage
◦ Tip contamination or damage
◦ Infection barrier

56
Q

Light-cure Composite
Types of curing units:
(4)

A
  1. Quartz-tungsten-halogen
  2. Plasma Arc
  3. Laser
  4. Light-emitting diodes (LED)
57
Q

Light-cure Variables
Procedural factors
(3)

A

◦ Exposure time
◦ Tip size: smaller tip= increase output, increase heat
◦ Distance: decrease Output when you increase
distance

58
Q

Light-cure Variables
Restoration factors
(3)

A

◦ Darker shades absorb light
◦ Smaller particles: increase light scatter
◦ Curing through tooth
- decrease output

59
Q

Curing Lights: Quartz tungsten halogen (QTH)
(4)

A

Usually tested with an 11 mm diameter light tip
◦ However, if a 3 mm diameter tip is used then the output can increase 8 fold which also can
heat up the tooth greater than the 5-8 degrees that can cause pulp cell death
Don’t touch the tip to the material being cured
At 6.0 mm distances from the restoration the output at the tip can be 1/3 what
it should be.
Never look directly at the light it can cause retinal damage.

60
Q

Light Curing: equipment factors
Factors that reduce light output
(4)

A

◦ Frosting of bulb, Light reflector degradation, Fiber optic bundle breakage
◦ Tip contamination by resin buildup - lower output
◦ Sterilization problems - frosting the tip
◦ Infection control barriers - need longer curing times

61
Q

Classified by Activation:
Dual-cure Composite
(2)

A

Both light and chemical activator/initiator systems present
Used under ceramic inlays, onlays, crowns
◦ Composite cement
◦ Accommodate thicker areas, light may not penetrate adequately

62
Q

Oxygen inhibited layer

A

~15 microns thick, on the outer layer which facilitates addition and wetting of
subsequent layers

63
Q

Just-cured composite may have –% of the unreacted methacrylate groups to
copolymerize with the newly added material

A

50

64
Q

Older restorations –

A

will fully cure over time, do not have the unreacted
methacrylate groups
◦ Repair strength will be 50% of the original restoration. (Roughen with diamond)

65
Q

Important Properties of Dental Composite
(7)

A
  1. Thermal expansion and contraction
  2. Sorption
  3. Surface finish
  4. Wear resistance
  5. Strength, elastic modulus
  6. Degree of Conversion
  7. Polymerization shrinkage
66
Q

Properties: Thermal Expansion Coefficient
With temperature change, materials
expand and contract
(2)

A

◦ Larger mismatch between tooth and
restoration, margins debond, microleakage
◦ Filler: low TEC; More filler, less expansion
& contraction

67
Q

Properties: Sorption
(3)

A

Water, saliva absorption, cause material to expand
Filler, silanation, and cross-linking the resin decrease sorption
Ideally want sorption to be ≤ 2%

68
Q

Finish and Polish:

A

Obtaining anatomic contours of composite resin after
placement

69
Q

Grinding –

A

gross cutting of excess material

70
Q

Finishing –

A

fine cutting

71
Q

Polishing -

A

final smoothing
◦ FINISH FIRST

72
Q

Surface Finish:

A

Particle Size Effect and detachment from resin matrix

73
Q

— best wear resistance

A

Microfill
◦ Related to small fillers and close filler spacing

74
Q

Newer hybrid materials similar wear resistance to —

A

microfills

75
Q

Additional Wear Factors:
(2)

A

◦ Maintain occlusal contacts on enamel
◦ Anterior < Premolars < Molars

76
Q

Increased filler, increased —

A

strength

77
Q

Microfill – Hybrids (all types)

A

<
◦ Microfill weakest, 40-60 wt% filler
◦ Often used over hybrid for optimum esthetic
surface
◦ Low stress areas

78
Q

As filler increases, Modulus (stiffness) —

A

increases
: less flexible

79
Q

Low modulus applications (abrasion lesions)
(2)

A

◦ Lower modulus of elasticity materials are better for Class V lesions because the tooth flexes.
◦ Microfill better here for class V lesions. A lower modulus material will flex a little and
compensate for flexural forces.

80
Q

High modulus,

A

MOD restoration, minimize cusp flexure

81
Q

Degree of Conversion (DC)

A

Measure of the % of carbon-carbon double bonds that have reacted
during polymerization reaction

82
Q

The higher the DC, (3)

A

better strength, wear resistance, decreased sorption.

83
Q

55-65% conversion

A

◦ With dimethacrylate system, does not mean that 40-50% of monomer
unreacted

84
Q

At 20% conversion a — is created

A

gel

85
Q

Polymerization Shrinkage
(3)

A
  1. Composite shrinks ~2% when it is cured
    a. Filler effect – when fillers are added, shrinkage is reduced because fillers don’t shrink
  2. Bis-GMA/TEGDMA Resin, ~10% shrinkage
  3. Linear vs ring-opening monomers
    ◦ Ring opening results in less shrinkage
    (<1%)
86
Q

With polymerization shrinkage, stress occurs at the composite-tooth
interface.
(2)

A

◦ Stress level will vary, depending on the type of restoration
configuration factor, C-factor
◦ C-factor = bonded/unbonded surfaces

87
Q

Highest stress is Class – restoration (~13-17 Mpa)

A

I

88
Q

Gap formed between adhesive and tooth

A

~ 5-20 microns

89
Q

Managing Polymerization Shrinkage/Stress
(3)

A

Incremental placement
◦ decrease bonded/unbonded, each increment
◦ Reduces STRESS
◦ Shrinkage remains the same

Self-cure composite
◦ Slower polymerization rate
◦ Internal flow, compensates for shrinkage

Low shrinkage composite
◦ Filtek LS 0.9% shrinkage
◦ Silorane resin, ring opening

90
Q

Resin matrix
(3)

A

◦ Polymerized resin is biocompatible
◦ Unpolymerized material (monomer) potentially cytotoxic, but poor
solubility
◦ Bis-phenol A, precursor of Bis-GMA is estrogenic

91
Q

Bis-phenol A, precursor of Bis-GMA is estrogenic
(3)

A

◦ Fetal reproductive anomalies, decrease sperm count,
increase proliferation cancer cells with estrogen receptors
◦ Controversy, is BPA present in composites?
◦ Initial studies indicate this is not a concern, but need more long-term evaluation, better
technology. As little as 1PPT CAN affect fish reproductive organs.

92
Q

Filler size
(2)

A

◦ Concern regarding the nanofillers and potential to cross cell
membranes
◦ Possible problem during restoration finishing and removal

93
Q

Size of filler can be smaller than a —

A

virus

94
Q

During finishing of composite
(3)

A

◦ finish under water spray and high-speed suction
◦ with a face mask on
◦ to avoid breathing the dust into yours and the patient’s lungs

95
Q

Bonding Agent
Primer/Adhesive Resin

A

◦ Resin matrix phase, unfilled
◦ Flows into etched dentin and enamel, micromechanical union
◦ Macro and micro resin tags, enamel
◦ 1-5 micron thick hybrid layer, dentin
◦ Co-polymerizes with the composite material
◦ Chemical union

96
Q

Chemistry game changer is 10-MDP Methacryloyoxy-decyl-dihydrogen-phosphate
Mechanism of action :

A

A monomer that chemically interacts via ionic bonding to calcium in
hydroxyapatite

97
Q

10-MDP (3)

A

Single bottle, no mix adhesive system
Can be used in total etch, self-etch or selective-etch mode (etch enamel only with phosphoric
acid and rest of tooth with universal adhesive)
Monomer is a phosphate ester

98
Q

Technique for Light-cured Composite
(8)

A
  1. Select shade prior to rubber dam
  2. Preparation (mechanical retention?) and caries removal
  3. Total Etch/2-step (1-bottle) adhesive:
    a. Etch 15 sec, Rinse 10 sec
    b. Blot excess water with brush or pellet
    Do not overdry
    c. Apply bond agent
    a. Dry 5 sec, evaporate solvent without drying tooth
  4. Light polymerize 20 sec (all areas cured)
  5. Place composite in ~2 mm increments
    a. Increments should not span across entire prep,  C-factor
    b. the first increment next to the pulp about 1 mm thick)
    c. Polymerize 20 sec; longer for darker shades or if curing through
    the tooth
    d. Protect material from extended exposure room and overhead
    light, will cause a premature set
    6.Minimize void formation
    7.Cure longer when curing through the tooth
  6. ie, curing the facial side of a distolingual restoration
    8.Overfill slightly, allow material for contouring, finishing and
    polishing
99
Q

Fracture Toughness
(3)

A

Similar to flexural strength except a notch is placed at the bottom of the
sample
Good test for composite property
Test with a flaw in material – the way restorations and life really is

100
Q

Glass Ionomer Materials
Many dental uses:
(5)

A

◦ Cements
◦ Liners and bases
◦ *Sealants
◦ Restorative materials
-Primarily Class V
◦ *Core buildup materials

101
Q

Acid-base reaction, results in Fluoride release
(3)

A

◦ Initial “burst” of Fluoride released, then very low-level release
◦ This level does not protect teeth from caries
◦ Needs to be “recharged” with fluoride to continue releasing at adequate levels to be protective

102
Q

Resin-Modified Glass Ionomer
Primary Use in Operative Dentistry:

A

Liner
◦ Vitrebond Plus
◦ Light cured
◦ Recommended when dentin is less than 2mm thick
◦ Liner layer should be no thicker than 0.5mm

103
Q

Resin-Modified Glass Ionomer
(4)

A

◦ Use as Restorative material
◦ Dual Cure
◦Indicated for Root Caries
◦ Ex. Equia Forte

104
Q

Polyacid Modified Composites
Compomers
(3)

A

◦ NO acid-base reaction with compomers
◦ This sets them apart from GI/RMGIs
◦ Ex. Geristore

Operative 2 (12 decks)

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