Prepolymerizing microfilled composite resins have gained acceptance as restorative materials. However, when used as a posterior material, many of them undergo debonding of the organic filler. Such a condition has been attributed to the fact that the filler particles are held to the surface of the resin matrix primarily by mechanical means. Recently, a composite resin has been developed in which the prepolymerized organic particle is bonded chemically to the resin matrix through copolymerization. The material con sists of trimethyol propane trimethacrylate, and the numerous double bonds on the surface provide a means for chemical bonding. A three-bodied wear-testing device was used in conjunction with a series of experimental trimethyol propane trimethacrylate-containing polymers, and it was shown that most of these systems offered greater resistance to wear and marginal deterioration than did conventional systems.