Biomaterials - Composite Flashcards
a physical mixture of 2 or more materials with superior properties as compared to the individual components.
Composite
________ uses:
- Tooth-colored restorative material
- Bonding agents (filler may be present)
- Sealants (filled)
- Composite resin luting agents (cement)
- Resin-modified glass ionomer material
Dental Composite Uses
Resin matrix phase reinforced by dispersed filler particle phase bound to the resin by a _____ coupling agent
silane
______:
◦Matrix in US products
Bis-GMA bisphenolA diglycidyl methacrylate
What is the filler particle in composite?
Crystalline silica
___;
◦Dispersed in resin matrix◦Distribution varies depending on the material
Filler
T/F: Matrix is not strong without fillers
True
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. don’t expand or contract
4.Improved workability, handling
5.DECREASED water sorption
6.INCREASED radiopacity(Barium, Strontium, Zirconium)
Filler
◦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
Silane
What is the initiator for light-cured composite?
Camphoroquinone
What is the initiator for self-cured composite?
Benzoyl peroxide
- 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.
Polymerization Inhibitor
_____ are optical modifiers used to great more esthetic and whiter restorations
Opacifiers
What are the 3 different ways discussed that are used to classify composites?
Filler particle size and size distribution
Handling characteristics
Type of polymerization
\_\_\_\_\_ and \_\_\_ fill composite: Not used much today Large fillers ◦Rough surface finish Not good size distribution ◦Increased inter-filler resin space, low wear resistance Prone to staining
Macro and midifill
\_\_\_\_\_\_ fill composite: Excellent finish, Best wear resistance Weakest Use for esthetic, low-stress sites ◦Class III ◦Layer over hybrid, kit systems Brands: Durafill VS, Epic TMPT, Renamel, Heliomolar
Microfill
_____ filler composite
◦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
Midi-micro Hyprid
_____ filler composite
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 strengthe.ClearfilAPX, 4-Seasons, Miris, Vitalescence, Synergy, Tetric, EsthetX
Mini-micro Hybrid
_____ filler composite
◦Nanometer: 10-9Micrometer: 10-6
◦Mix of mini, and nanofillers,0.1-1 and 0.001-0.01 m (1-10 nm)
◦~80 wt%
◦Newest materials: FiltekSupreme 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
Mini-nano Hybrid
What are the 2 classifications based on handling characteristics?
Flowable
Packable
______ composite
Low viscosity hybrid
reduced filler,
40-60 wt%, adapts better without handling
Many are not radiopaque
◦Big problem= difficult to distinguish from recurrent caries
Flowable
What are the 3 filler materials used to make a flowable composite more radiopaque?
Barium
Strontium
Zirconium
Does flowable or hybrid composite have more shrinkage?
Flowable
Does flowable or hybrid composite have more stress?
Hybrid
____ fill of composite
Newer technology
-Need high output lights ~ 1000 Mw/cm2
Are highly filled with more translucent fillers (which do not shrink) and less resin matrix (which shrinks)
◦Higher filled have more stress because there is less resin to relieve the stress when it cures
Uses methacrylate monomers
Addition fragmentation monomer (AFM) and aromatic urethane dimethacrylate(AUDMA) work together to provide stress relief without compromising wear resistance.
bulk fill
_______ composite
Mini and midi fillers, >80 wt%
Supposed to handle like amalgam
Packable
____ cure composite is cured with blue light activators
LIght-cure
\_\_\_\_\_\_ composite: 2-paste system, 1 with activator, 1 with initiator ◦Mixed to begin polymerization Advantage: bulk placement Disadvantages ◦Mixing, incorporate bubbles, decrease strength ◦No control of working time ◦Amine, not color stable
Self cure Composite
\_\_\_\_\_ composite: One-paste system Activator: Blue light (~470 nm)Initiator: ◦Camphorquinone(CQ), photoinitiator ◦DMAEMA, alphiaticamine (accelerator)
Light-cure Composite
Advantages
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
Disadvantages
a.Limited light penetration, ≤ 2mm increments, 20 sec
b.Blue light, retina damage –use orange shield
Light cure composite
What are the 2 main types of curing units mentioned?
Quartz-tungsten-halogen
Limit-emitting diodes (LED)
- Starts low intensity, intensity increases over time of cure
- The theory is that a soft cure can allow some stresses to be relieved in the composite resin before it reaches the gel stage;forms stronger long-chain polymers, decreases polymerization shrinkage
soft start or ramp cure
Both light and chemical activator/initiator systems present
Used under ceramic inlays, onlays, crowns
◦Composite cement
◦Accommodate thicker areas, light may not penetrate adequately
Dual-cure Composite
~15 microns thick, on the outer layer which facilitates addition and wetting of subsequent layers.
Just-cured composite may have 50% of the unreacted methacrylate groups to copolymerize with the newly added material
Older restorations –will fully cure over time, do not have the unreacted methacrylate groups
◦Repair strength will be 50% of the original restoration. (Roughen with diamond)
Oxygen inhibited layer
What are the 7 important properties of dental composite?
- Thermal expansion and contraction
- Sorption
- Surface finish
- Wear resistance
- Strength, elastic modulus
- Degree of Conversion
- Polymerization shrinkage
Is thermal expansion coefficient higher or lower with more filler?
Lower
If there is more filler in a composite, is there more or less sensitivity and contraction/expansion?
Less
Water, saliva absorption, cause material to expand
Filler, silanation, and cross-linking the resin decrease it
Ideally want it to be ≤ 2%
Sorption
Finish and Polish: Obtaining anatomic contours of composite resin after placement
Surface finish
Which fill has the best wear resistance?
Microfill
How does filler relate to flexural strength?
INcreased filler increases strength
As filler increases, Modulus (stiffness) _____
Increases
The higher the ____, better strength, wear resistance, decreased sorption.
Degree of conversion
Composite shrinks ~___% when it is cured
2%
when _____ are added, shrinkage is reduced because they don’t shrink
fillers
_____ is the ratio of bonded surfaces to unbonded surfaces
C factor
Increasing C factor has what effect on stress and shrinkage?
Increases
___________ is potentially cytotoxic, but poor solubility
Unpolymerized material (monomer)
◦Concern regarding the nanofillers and potential to cross cell membranes◦Possible problem during restoration finishing and removal
Filler size
Size of filler can be smaller than a virusDuring finishing of composite◦finish under water spray and high speed suction◦with a face mask on ◦to avoid breathing the it into yours and the patients lungs
Dust
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◦
Primer/Adhesive Resin
Can be used in total etch, self-etch or selective-etch mode
Universal adhesives
What increments of composites should be placed to decrease C factor?
2 mm
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
Fracture Toughness
