Wear rates of posterior composite resins.

The wear rates of nine posterior composite resins were determined for a period of up to 3 years. The wear rates observed depended on the method used for evaluation. A quantitative method of evaluation showed that the wear rates decreased with time. With the use of the quantitative measurements obtained at the end of 6 months after insertion, it was possible to predict the average annual rates of wear at the end of 3 years.