Composite Flashcards
3 components of composite
1) highly cross-linked polymeric matrix (organic)
2) fillers (inorganic)
3) silane coupling agent
example of polymerization inhibitor
butylated hydroxytoluene (BHT)
high density monomers
Bis-GMA
UDMA
added to bis-GMA to decrease viscosity
TEGDMA
high density makes it ___
viscous and difficult to manipulate
Bis-GMA and UDMA cause increase in what?
increase in:
- polymerization shrinkage
- strength, rigidity
- cross linking
the greater the proportion of diluting monomers, the greater the _____
the greater the polymerization shrinkage
function of fillers
- reinforcement
- reduction of polymerization shrinkage
- reduction of thermal expansion/contraction
- decreased water sorption
- control of workability/viscosity
- imparting radiopacity
quartz
- chemically inert
- abrasive
- hard to grind
- hard to polish
silica
- not crystalline
- not as hard as quartz
- less abrasive and easier to polish
barium
-most common
-radiopacity
-not as inert
slowly leached and weakened in acidity, alkalinity, oral fluids
glass fillers
- attacked by fluoride solutions
- susceptible to abrasive wear
- less lifetime (compared to silica resins)
distribution of fillers
various particle sizes allow max loading (fewer spaces)
coupling agent
bonds filler particles to resin matrix
commonly used coupling agent
organosilanes
when would you use a microfilled composite resin
restoring lesions on smooth surfaces but NOT stress-bearing situations
resin with elongated fillers and spheroidal particle fillers at different sizes (both microfine and fine)
hybrid composite
better polishing than macrofilled composites, bit harder
small particle composites
smaller, no surface roughing problem, better translucency
microfilled composite
why do microfilled composites chip a lot
the bond between composite particles and cured matrix is weak
better at high stress sites but also esthetic, contains colloidal silica and ground particles of glass with heavy metals
hybrid composite
individual particles are surface coated FIRST, then put in chain
prevents agglomeration and high viscosity
nanofilled composite
