L4 Resin based composite Flashcards
what is the composition of a resin based composite “?
1.) resin component
2/) reinforcing fillers
3.) saline coupling agents
4.) initiator ( light activator )
5.) inhibitor
6.) optical modifires
what is the resin matrix made up of?
bis-GMA
UDMA
TEGMA
what factors play a role in increasing viscosity during setting process?
size of monomer and co-polymer
which component of the resin matrix is extremely viscous ?
bis-GMA
why is UDMA and TEGMA added to resin matrix ?
to decreases bis-GMA resin vescocity and increase degree of converstion
why is UDMA and TEGMA added to resin matrix ?
to decreases bis-GMA resin vescocity and increase degree of converstion
what are resin composites classified based on?
their filler particle size
what are the major roles of filler components ?
reduce amount of resin matrix which helps control shrinkage of composite during polymerization
increase hardness and strength
reduce wear , water sorption and staining
increase viscosity
- Filler are radiopaque so radiopacity for visualization on x-ray
what is the % of filler particles by weight and by volume
by volume 30-70%
by weight 50-85%
what is the function of a coupling agent ?
binds resin matrix and filler particles together .
roles and benefits of filler particles can only be achieved if it is coupled strongly with resin matrix
what is a common light activator and what wavelength is used to activate it ?
camphorquinone , activated by visible blue light (400-500nm) 468
what is an inhibitor commonly used in light activated composites
?
butylated hydroxytoluene
what is the role of an inhibitor ?
prolongs shelf life of product
prevent propagation and reacts with free radicals
ensure sufficient working time and extend resin storage life
what is the role of optical modifiers ?
materials used to help achieve desired shade by adding small amounts of metal oxide ( aluminum and titanium dioxide)
darker shades should be applied in thinner layers
how are both chemically (self-cured) and light activated composites polymerized?
through action of free-radical polymerization and addition reaction
how many pastes are used in the chemically activated composites ? and how many are used in the light cured system ?
it is a two paste system while light cured systems only use one paste
what reaction occurs in light cured composites in order to start initiation ?
camphor quinone reacts with amine activator in order to form free radicals. these free radicals then break double carbon bonds to start process of polymerization
what is the typical degree of conversion ( from monomer to polymer ) when using resin based composie?
50-70%
what is the C(configuration) factor ?
ratio of bonded to unbonded walls . indicates potential for development of stress
what is the thermal conductivity and expansion of resin composites when contrasted with enamel and dentin ?
thermal conductivity is almost the same while thermal expansion is slightly more than that of enamel and dentine
mechanical properties of resin composite is dependent on ?
filler content and type , and the efficiency of the coupling agent ( most composites have good mechanical properties but fail in tension )
how do resin composites attach to the tooth ?
via mechanical bonding
what is the minimum bond strength required to prevent marginal gap formation?
20Mpa
what is the composition of a resin based composite “?
1.) resin component
2/) reinforcing fillers
3.) saline coupling agents
4.) initiator ( light activator )
5.) inhibitor
6.) optical modifiers
how is composite bonding achieved ?
acid-etch technique
chemical adhesion
single bottle system
what type of filler has the highest wear resistance ?
Mirco-hybrid have highest wear resistance
what material is most likely going to be used to fix anterior teeth for aesthetic reasons >?
resin based composite because they have a Varity of shade options and good marginal adaptations
what is a flowable composite ?
Hybrid composite with reduced filler level
and a narrower particle-size distribution to increase flow and
promote intimate adaptation to prepared tooth surfaces. Flowable composites are often used as the first layer of a cavity filling
to improve filling adaptation to the cavity.
