Biomaterials: Composite Resin Flashcards
What tooth-colored materials were around in 1870s?
silicate cement
- high solubility
- severe surface wear
- low mechanical properties
What tooth-colored materials were around in 1940s?
polymethylmethacrylate (PMMA)
- initially unfilled: high curing shrinkage
- high thermal expansion and contraction
- stress at the cavity margins
What tooth-colored materials were around in 1960s?
composite resin
- fillers bonded
- improved properties: low thermal coefficient of expansion, higher wear resistance, improved clinical performance
What is the definition of composite?
material containing at least two components (phases) with distinct chemical and physical properties that after blended, they show unique and superior properties as compared to the individual components
What do you use composite for?
- Tooth-colored restorative material (direct or indirect rest. technique)
- Bonding agents (filler may be present)
- Sealants (filled)
- Composite resin luting agents (cement)
- Resin-modified glass ionomer material
- Light-activated liner materials
- CAD/CAM blocks
- Resin endodontic sealers, etc.
What are the components of dental composite?
- Resin matrix
- Filler particles
- Coupling agent
- Activator-initiator system
- Pigments and other components
What are the different types of resin matrix?
- Bis-GMA (most used)
- UDMA
- TEGDMA
What are the characteristics of filler particles in composite resin?
- crystalline silica quartz (Ba, Li, Al silicate glass, amorphous silica)
- dispersed in resin matrix
- distribution varies
What are the benefits of filler particles?
- Reinforcement of the resin matrix
- decreased polymerization shrinkage
- decreased thermal expansion
- viscosity control
- decreased water sorption
- increased radiopacity
What does the coupling agent (silane) allow for?
better stress distribution between resin matrix and filler particles
What are the two types of initiators?
for chemical/self-cure
- benzoyl peroxide
for light-cured
- camphoroquinone
- DMAEMA (amine)
What are the two types of activators?
for chemical/self-cure
- tertiary amine
for light-cured
- blue light (465 mn)
What is the benefit of polymerization inhibitor?
✓ Prevent spontaneous polymerization
✓ Stop polymerization from brief room light exposure (reacts with free radicals)
✓ Increase the shelf-life of the composite resins
What are examples of polymerization inhibitor?
butylated hydroxytoluene (BHT)
hydroquinone
What are some optical modifiers for composite resin?
- pigments: metal oxides
- opacifiers: titatnium/aluminum oxide
What are the different filler sizes?
- Macrofill
- Midifill
- Microfill
- Hybrids
a. Midi-Micro Hybrid (Midi- or Microhybrid)
b. Mini-Micro Hybrid (Microhybrid)
c. Mini-Nano Hybrid (Nanohybrid)
What are the characteristics of macrofill/midifill?
- large fillers
- poorly distributed
- prone to staining
- not used much anymore
What are the characteristics of microfill?
- excellent finish
- low mechanical and surface properties
- esthetic, low-stress areas
What are the characteristics of hybrid composite filler Midi-Micro hybrid?
- improved surface finish (compared to macro/midi)
- high strength
- many of the current materials
What are the characteristics of mini-micro hybrids?
- smoother finish
- slightly lower strength than midi-micro hybrids
What are the characteristics of mini-nano hybrids?
- newest material
- strength is comparable to mini-micro hybrids
- finish is equivalent to midi-micro hybrids
What are the three classes of composite based on handling characteristics?
- Packable (Conventional/Regular)
- Flowable
- Bulk fill
What are the characteristics of packable composite?
✓ Regular or conventional
✓ Medium viscosity
✓ Macrofill, microfill, hybrid, nanohybrid…
✓ Most widely used
What are the characteristics of flowable composite?
✓ Low viscosity - reduced filler content; 40-60 wt%, adapts better without handling
✓ Lower filler percentage, decreased modulus, increased flexibility
✓ Used under conventional composite at gingival floor of Class II
Many are not radiopaque
✓ Big problem= difficult to distinguish from recurrent caries
✓ Distinguish between composite and recurrent caries
✓ Barium,strontium, zirconium filler
What are the characteristics of bulk fill?
✓ To avoid incremental placement (“one bulk placement”)
✓ Highly filled with pre-polymerized particles
✓ Larger size fillers (reduces the light scattering)
✓ more translucent filler particles (increases the light penetration and polymerization)
✓ 5 mm increments
✓ Need high output lights ~ 1000 mW/cm2
What are the characteristics of condensable composite?
✓ Packable with high viscosity
✓ Mini and midi fillers, >80 wt%
✓ Supposed to be handled like amalgam (amalgam alternatives in the market)
✓ Bulk cure inadequate
✓ Not well-accepted
What are the advantages and disadvanges of chemical cure?
✓ Advantage: bulk placement
✓ Disadvantages: Mixing (incorporate bubbles, decrease strength); No control of working time; Amine (not color stable)
What are the advantages and disadvantages of light cure?
✓ Advantages:
-Mixing not required, less porosity, increased strength.
-Aliphatic amine (DMAEMA) more color stable than self-cure aromatic tertiary amine
-Better control of working time
✓ Disadvantages:
-Limited light penetration
- ≤ 2mm increments, 20 sec
-Blue light, retina damage – use orange shield
What are the steps of the polymerization reaction?
activation
initiation
propagation
termination
What are some light-cure variables?
- exposure time
- tip size: smaller tip = increase output, increase heat
- darker shades absorb light more
- smaller filler particles increase light scatter
- curing through tooth decreases output
What happens to the output when you increase the distance when light-curing?
decreased output
What are the different types of curing units?
- Quartz-tungsten-halogen
- Plasma Arc
- Laser
- Light-emitting diodes (LED)
What are the characteristics of the quartz-tungsten-halogen (QTH) light curing machine?
✓ QTH source consists of a tungsten filament that is surrounded by a clear, crystalline quartz bulb containing a
chlorine-based halogen gas.
✓ Broad emission spectrum (~400 to 500 nm)
✓ Cooling system is noisy
✓ Relatively low irradiance
✓ Heating in the output (pulp cell damage) – don’t touch the tip
✓ Retinal damage (Never look directly at the light)
What are the characteristics of the plasma-arc light (PAC) light curing machine?
✓ Broad emission spectrum (390 to 510 nm)
✓ High radiant power and high irradiance
✓ PAC lights are expensive
✓ Noisy, large, not portable, cannot be battery operated
✓ Become less popular with the introduction of LED curing lights
What are the characteristics of the argon-ion laser light curing machine?
✓ High irradiance in only 10 seconds
✓ Produces several intense and narrow emission peaks
✓ Argon-Ion Lasers are expensive
✓ Become less popular with the introduction of LED curing lights
What are the characteristics of the light-emitting diodes (LED) light curing machine?
✓ Introduced in the 1990’s
✓ Many advantages:
- solid state, lightweight, battery driven
- more efficient (at least 10 times more than QTH)
-extremely long working life
✓ First and second generation: relatively narrow emission
spectrum
✓ Third generation: Multiwave, Multipeak, Polywave
What can reduce the light curing output?
- Degradation (light reflector, fiber optic bundle, bulb)
- Tip contamination by resin buildup - lower output
- Sterilization problems - frosting the tip
- Infection control barriers - need longer curing times
What is the oxygen inhibited layer?
15 microns thick, on the outer layer which facilitates addition and wetting of subsequent layers
What are the problems with deficient polymerization?
marginal staining
microleakage
secondary caries
enamel microcracks
disadaptation
increased wear
postoperative sensitivity
bulk fracture of the restoration
release of chemicals
What are the important properties of dental composite?
- Polymerization shrinkage and stress
- Wear resistance
- Surface finish
- Marginal infiltration
- Water Sorption
- Radiopacity
- Color stability
What is the C factor?
Stress level will vary, depending on the type of restoration configuration factor
What does incremental placement do to the C factor?
decrease
- stress is reduced
What is important about wear resistance?
✓ Biofilm formation = bacterial acids = soften of resin matrix
✓ Higher filler amount = higher wear resistance
What is important about surface finish?
✓ Type and size of filler
✓ Lower filler size = higher surface finish
What is important about marginal infiltration?
✓ Decreased with improvement of adhesive systems
✓ Failure “gap” between tooth and composite
✓ Secondary caries, marginal staining and fracture, post-operative sensitivity
What is important about water sorption?
✓ Lower filler amount, higher water sorption = higher expansion
✓ BisGMA and TEGDMA: higher sorption as compared to UDMA
What is important about radiopacity?
✓ Important to distinguish carious tissue and marginal adaptation, air bubbles (defects)
What is important about color stability?
✓ Color change after 2-5 years
✓ Food, smoking, beverages
What are bonding agents?
agents that bond micromechanically or/and chemically the restorative material (or luting agent) to tooth substrate through an interface
What is the purpose of acid etching?
◦ To remove the minerals from dental substrate (micro-retentions on enamel and exposing the collagen matrix)
◦ Allowing the adhesive infiltration
What is the mechanism of action of the universal adhesives?
A phosphate monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
