The hardness of composites as a function of temperature

The microhardness of conventional, posterior and microfil composites were measured as a function of temperature in an aqueous environment. With the exception of one posterior composite and two microfils, the composites suffered dramatic decreases in hardness (of the order of 30-50%) over temperature intervals corresponding to that encountered in oral service. In those systems which did not display hardness changes, interactions between glass and matrix as well as enhanced filler packing may be important.