Chapter 6,7,8 Flashcards
____ are the most frequently placed direct restorations
Composites
First tooth color restorative material
Silicate cement
Bis-GMA
resin monomer developed in 1962. Added silica particles to reinforce it and make it more resistant
Choosing a material depends on
- extent of damage
- Stress places on the tooth
- Esthetic requirements of the patient
composite
a mixture of 2 or more materials with properties superior to any single component
Composite resins
tooth-colored restorative materials, that can be placed anywhere in the mouth
- composed of mainly organic resin matrix and inorganic filler particles joined together by a silane coupling agent.
- initiators and accelerated are added to set the material as well as pigment to give color
Most commonly used resin for the organic matrix of composites
bis-GMA
- urethane dimethcrylate is another used resin
Adding filler particles to the organic resin make the composite
stronger and more wear-resistant
-also by reducing the amount of resins filler help reduce the amount of shrinkage that occurs when the resin sets
- also reducing the amount of resins reduces thermal expansion and contraction and decreases water sorption (sorption causes resins to soften and more likely to wear)
Composites on radiographs
Heavy metal ions are added to composites, to make them wooer radiopaque
-barium, lithium, or strontium
-older composites show radiolucent
Important factors for durability of composites
- size of filler particles
- ratio or weight of the filler matrix
- (higher resin= low filler)
Wear of the composite is related to
- filler particle size
-the amount of filler
-amount of resin between filler particles
Larger filler particles
Tend to get pulled from resin matrix at the surface (plucking) when the restoration is under function or abraded by food and tooth brushing, resulting in wear and a rough surface
coupling agent
Is used to provide a stronger bond between inorganic fillers and the resin matrix
-Silane is the agent
- good adhesion is necessary to minimize the loss of filler particles and reduce wear
pigmented resins can be used to
-cover discolorations or dark dentin
- Hide graying effect of a metal post in a RCT tooth
Polymerization
A chemical reaction the occurs when resin molecules join together end-to-end to form a long chain-molecules to polymers
Chemical/ self cure
two paste system
1. base, contains composite and benzoyl peroxide as an initiator
2. Catalyst, contains composite and tertiary amine as an activator
- equal parts
-inhibitors are added to each paste to slow down the reaction - carriages with mixing tips mix pastes as they are distributed
Light cure
most common type
preferred because it requires no mixing and the operator can control working time
The depth of cure in 2mm
contain inhibitor to prevent premature setting due to oratory light
Dual cure
area not able to be reached by the blue continues to set
-endodonically treated teeth and placing composite core material in a canal space
Filler sizes
- Macrofilled
-Microfiller
-Hybrid- Microhybrids
- Nanohybrids
- Universal composites
-Nanocomposites
Composites over time
- Filler size has become smaller
-number of particles has increased - polymerization shrinkage has decreased