Resin based Dental composite materials Flashcards
What causes composite degradation?
Composite degradation is caused by spaces forming between polymeric chains leading to composite absorbing water. Water enters the composite and attacks the coupling agent which starts to fail leading to breakdown of the composite material.
What is the biggest problem with resin-based composite filling?
Polymerization this is countered by adding filler material
What is the function of filler when used with resin based composite?
Decrease contribution of bad matrix using filler. Matrix is weak, easily scratched.
What can saliva do to the filling?
Water causes discolouration
Water can cause filling to expand
Saliva has stress enzymes which can cut the polymeric chain
How is resin-based composite designed not to fail?
Composite has high resistance to crack propagation
What is the ideal kind of elastic modulus for dental fillings?
If material rigid the stress passes with high magnitude to underlying structure, so a low elastic modulus is more ideal for filling
What do smart materials do?
Smart material “senses” pH change which results in release of fluoride in response to low pH.
What are the 2 ways for colour to be changed of composite?
2 ways for colour to be changed
Taking in pigmentation of surrounding environment
Accumulation of plaque
What are homogenous and heterogenous composites?
Homogenous composite means all fillers are the same.
Heterogenous composite means fillers are different in size
Why is working time for composite limited?
Composite is affected by ambient light.
What light is used for composite material curing?
Visible light
How long do you expose composite to light during curing?
20 seconds. Curing maximal at 40 seconds.
