Resin Composites Flashcards
What is a resin composite?
a combination of 2 chemically different materials with a distinct interface separating the components.
What are resin composited used for?
tooth coloured fillings
What is the earliest direct tooth coloured restorative material called?
Forerunner’s silicates
What is the setting reaction of forerunners silicates?
aluminosilicate glass + phosphoric acid = salt and water
Where are acrylics derived from?
products used to make dentures
What type of set do acrylics have?
chemical
In resin composite, what is the resin matrix usually based upon?
methyl methacrylate or dimethacrylate monomers
What are the 3 components of the resin matrix?
- Methacrylate/ dimethacrylate monomer
- Comonomers i.e., TEGMA
- Inhibitors
What reaction occurs in retained acrylics in resin composites?
free radical polymerisation
What is polymerisation triggered by?
light curing
What do fillers have to be coupled with?
coupling agent
What are coupling agents used for?
improve the adherence of resin to filler surface
What is the purpose of fillers?
reduce shrinkage
What is the name of the coupling agent in resin composites?
vinylsilate
What is silane?
a filler
What happens to surface hardness as filler content increases?
surface hardness increased
What happens to volume when filler is added?
decreases percentage volume by setting
What happens to thermal expansion when filler is added?
thermal expansion decreases
What is the visible blue light used to set resin composites called?
camphorquinone
What do all resin composites contain?
resin
filler
coupling agent
What are resin and filler useless without?
coupling agent
What is the role of coupling agent?
transfers the stress generates under loading from the rigid and brittle filler to the more flexible and ductile polymer matrix
What are the 4 types of resin composites based on filler particle size?
- conventional
- microfilled
- hybrid
- nanocomposites
What must the properties of resin composite conform to?
ISO 4049
What happens to viscosity on leaving the tube?
increases
What are the disadvantages of resin composite?
may stain as resin matrix can take up fluids e.g., wine
What influences the overall success of a restoration?
cavity shape
What is C factor?
number of bonded surfaces/ number of un-bonded surfaces
What does C factor relate to?
shrinkage
What type of setting occurs in resin composite?
exothermic
What can trapped air pockets in resin composite result in?
inhibition of polymerisation and softens the matrix
What are nanofillers?
fillers with particle sizes ranging from 1-1nm
What is the optimum absorption of camphorquinone?
460-480nm
What happens when composite cures?
contraction
What are the 3 mechanisms influences by chemical effects?
- abrasive
- erosive
- fatigue
What is the name of the coupling agent?
vinylsilane
