Composites Flashcards
What is a composite?
Reinforced polymer matrix system used for restoring hard tissues
What are the applications of composites?
Esthetics, high stress areas
*nanocomposites can be used for both
What 3 factors are used to classify dental composites?
1-Shape
2-Particle size
3-Particle-size distribution of the filler
What resin matrix is most often used for composites?
dimethacrylate (better shrinkage control)
What is another low-shrink monomer used in resin composites?
Silorane (reduces shrinkage and internal stress build-up resulting from polymerization
What are three common fillers used in composites?
- Quartz
- Glasses (such as barium or zinc)
- Sol-gel derived ceramics
Macrofill composites contain _________ particles while hybrid and micro hybrid use __________ particles
larger (20-30 um), smaller (.04-1 um)
What are the two types of oxide nanoparticles?
- Nanofill (1-100 nm)
- Nanohybrides (0.4- 5 um) not a true nano filled composite*
Providing a good bond during setting is achieved by using what?
Coupling agents (most often silane)
*provides a hydrophobic environment to minimize water absorption of the composite
Polymerization Initiation is achieved by blue light at what wavelength?
465 nm (absorbed by camphorquinone)
What are the three stages of polymerization?
1-initiation
2-propagation
3-termination
How are composite polymer networks formed?
Free radical addition polymerization of methacrylate monomers (shrinkage as the molecules come together
What are three ways to decrease shrinkage during composite polymerization?
1-use silorane based composites
2-place composite in 2 mm increments
3-special adhesives
Why can it be hard to find composites on a radiograph?
many of the common fillers etc. are not radiopaque
Glass ionomer fused with metals such as gold, silver, titanium and silver are called what?
Cermets
