Week 5 Biomaterials Flashcards
what are the ways to classify composites
-filler particle size and distribution
-handling characteristic
-activation/type of polymerization
what is the history of tooth colored materials
-1870s silicate cement: high solubility
-1940s polymethyl methacrylate (PMMA)
-composite resin 1960s
what is composite
material containing at least 2 components (phases) with distinct chemical and physical properties that after blended, they show unique and superior properties as compared to the individual components
what is dental composite
resin matrix phase reinforced by dispersed filler particle phase bound to the resin by a silane coupling agent
what are the uses for dental composite
-tooth colored restorative material
-bonding agents
-sealants
- composite resin luting agents
- resin modified glass ionomer material
-light activated liner materials
-CAD/CAM blocks
-resin endodontic sealers
what does dental composite packaging consider
protection against visible light and moisture, allows oxygen though
what are the components of dental composite
-resin matrix
- filler particles
-coupling agent
-activator-initiator system
-pigments and other compounds
what makes up the resin matrix
-Bis GMA
-UDMA
-TEGDMA
what are the filler particles
crystalline silica, Ba, Li, Al silicate glass, amorphous silica
what are the benefits of filler particles
-reinforcement of resin matrix
- decreased polymerization shrinkage
- decreased thermal expansion and contraction
- viscosity control
-decreased water sorption
- increased radiopacity
what does higher filler amount reduce
the thermal expansion and contraction coefficients
reduced polymerization shrinkage is proportional to…
filler volume
what does the coupling agent do
strongly binds the filler to the resin matrix
what are the benefits of coupling agent
-better stress distribution between resin matrix and filler particles
- improves the mechanical properties
- decreased water sorption along filler resin interface
activator + initiator = _____
free radicals
composites: monomers to be converted into ____
polymers
what is the process of monomers to polymers triggered by
free radicals
what are the steps in reaction of polymerization
-activation
- initiation
-propagation
-termination
what does the polymerization inhibitor do
-prevent spontaneous polymerization
-stop polymerization from brief room light exposure
- once the blue light is used, all inhibitor quickly consume - polymerization chain reaction starts
- increase the shelf life of the composite resin
what are examples of polymerization inhibitors
BHT and hydroquinone
what are the optical modifiers
-pigments: metal oxides
-opacifiers: titanium and aluminum oxide
what are the classes of filler size and dsitribution
-macrofill
-midfill
-microfill
-hybrids
describe macrofill and midifill composites
-large fillers
-not good size distribution
-prone to staining
describe microfill composite
-excellent finish
- low mechanical and surface properties
-use for esthetic, low stress sites
describe hybrid composites (midi-micro)
-imrpoved surface finish
-high strenght
- universal composites
describe hybrid composites (mini-micro)
-newer material
- smoother finish
- slightly lower strength
what are the brands of macrofill and midifill
adaptic and concise
what are the brands of microfill
durafill VS, epic TMPT, renamel, heliomolar
what are the brand of midi-micro hybrid fill
TPH
what are the brands of mini-micro hybrid fill
-EsthetX
what are the brands of mini-nano hybrid fill
filtek supreme ultra
what are the classifications by handling characteristics
-flowable
- packable
describe flowable composite
-low viscosity hybrid reduced filler
- 40-60% adapts better without handling
- lower filler percentage, increased flexibility
- many are not radioopaque
when are flowable composites used
under conventional composite at gingival floor of class 2
why is lack of radiopacity a problem
difficult to distinuguish from recurrent caries
what is flowable composite made of
barium, strontium, zirconium filler
compare flowable vs packable
-flowable: more shrinkage, less stress
-packable: higher filler, high or medium viscosity, high stress
what increments do you used bulk fill in
5 mm
describe bulk fill
-pre-polymerized particles, higher size fillers
- more translucent filler particles
what are the classes of polymerization activation
-self-cure
-light cure
-dual cure
what are the advantages and disadvantages of light cure composite
- advantages: mixing not required, less porosity, increased strength. aliphatic amine more color stable than self cure. better control of working time
-disadvantages: limited light penetration, greater than 2 mm increments, 20 sec. blue light, retina damage- use orange shield
what are the procedural factors for light cure variables
-exposure time
-tip size- smaller tip = increase output, increase heat
- distance: decrease output when you increase distance
what are the types of curing units
-quartz-tungsten-halogen
- plasma arc
- laser
- LED
what are the factors that reduce light output
-degradation
-tip contamination by resin buildup
- sterilization problems
- infection control barriers
describe the oxygen inhibited layer
15 microns thick, on the outer layer which facilitates addition and wetting of subsequent layers
just cured composites may have 50% of the ____
unreacted methacrylate groups to co-polymerize with the newly added material
do older restorations have unreacted methacrylate
no
what are the important properties of dental composite
-polymerization shrinkage and stress
- wear resistance
-surface finish
- marginal infiltration
-water sorption
-radiopacity
-color stability
what does the polymerization yield
shrinkage and consequently stress at the composite tooth interface
what does stress level vary by
the type of restoration configuration factor, C-factor
what is C-factor
bonded/unbonded surfaces
higher c-factor, higher ____
stress
what is c factor in incremental placement
low
is shrinkage reduced in incremental placement
no stress is reduced
what is the polymerization rate of self cure composite
slower
do composites shrink towards the light in light directed polymerization
no
biofilm formation =
bacterial acids = soften of resin matrix
higher filler amount =
higher wear resistance
what is marginal infiltration decreased with
improvement of adhesive systems
where is the failure gap in marginal infiltration
tooth and composite
what happens in marginal infiltration
secondary caries, marginal staining and fracture, post op sensitivity
lower filler amount and higher water sorption =
higher expansion
which has higher absorption BisGMA and TEGDMA or UDMA
BisGMA and TEGDMA
when does color change
2-5 years
what causes color change
food, smoking, beverages
what are adhesive systems
agents that bond micromechanically or/and chemically the restorative material to tooth substrate through an interfacr
what are adhesive systems
agents that bond micromechanically or/and chemically the restorative material to tooth substrate through an interface
what does etching do
-to remove the minerals from dental substrate exposing the collagen
- allowing adhesive infiltration
what does bonding do
-adhesive application- infiltration
- encapsulation of dentin collagen matrix
- after polymerization: micromechanical interlocking
-outer layer co-polymerizes with composite material
what is the mechanism of action in chemical bonding
a phosphate monomer that chemically interacts via ionic bonding to calcium in hydroxyapatite
