Wear patterns and rates of posterior composite resins

The use of composite resins as posterior restorative materials has been growing at a rapid rate. In spite of major improvements in both physical and mechanical characteristics secondary caries and resistance to wear are still major concerns. This paper deals with the wear rate and patterns of wear of posterior composite resins. Results of long term clinical studies show that a major difference exists between composites containing submicron or supramicron sized filler particles. In general, the wear rates of the larger filler particles composite resins decrease with time. On the other hand, the microfilled posterior composite resins appear to exhibit a linear rate of wear. The wear patterns of the two different types of posterior composite resins are also dissimilar. Composite resins containing filler particles larger than 1 micron tend to undergo a generalized loss of material. The microfilled composite resins also lose material generally but to a lesser degree. Furthermore, the submicron filled posterior composite resins tend to exhibit localized wear, particularly in centric holding areas. Such a change does not, as a rule, occur with composite resins containing larger filler particles. Finally, the microfilled composite resins tend to develop continuous marginal fractures at tooth restoration interfaces.