Stability of radicals in cured composite materials.

During the radical polymerization of dental composites, the monomers polymerize to form a three-dimensional network containing remaining double bonds and free radicals. At 37 degrees C, these radicals decompose logarithmically with a half-life of 2-5 d. In this study, the half-life of radicals in a light-cured inlay composite was determined at different temperatures, and the influence of different fillers and filler amounts on the stability of these radicals in light-cured experimental composites was investigated. There is a strong logarithmic relationship between the half-life of the radicals and temperature. At a constant temperature, the half-life of radicals depends on the type of filler, the filler fraction, and the filler surface treatment. The stability of radicals determines to a great extend the adhesion of one composite to another, such as the adhesion of a luting cement to an inlay material.