Effects of temperature on mechanical properties of composite dental restorative materials.

In the oral environment, dental restorative materials are exposed to temperatures ranging from 10 degrees to 50 degrees C. Since the properties of many polymeric materials are sensitive to temperature of this magnitude, it is important to define the effects of service temperature on the mechanical properties of polymer matrix dental composites. Six commercial composites were tested in compression at 11 temperatures, ranging from 2 degrees to 80 degrees C. The volume fraction of filler particles in the materials is either 0.45 or 0.55, and they contain a range of particle sizes and particle compositions. The tests show that ultimate strength decreases linearly with increasing temperature. Strength is higher for the lower volume fraction material and is decreased by the presence of a small percentage of very large particles. Elastic modulus and yield strength decrease sigmoidally with increasing temperature and depend only on particle volume fraction. In the clinically significant temperature range, ultimate strength decreases 14%, the decrease in elastic modulus is either 6 or 11%, and the yield strength decreases 45%. The data show that the temperature conditions of the oral environment can significantly affect the mechanical properties of composite dental restorative materials.