Assessing the effect of composite formulation on polymerization stress

Background. In this study, the authors measured the magnitude of the polymerization stress of a variety of dental composite materials and explored the effect of a novel monomer, a methacrylated derivative of styrene-allyl alcohol, or MSAA, in reducing polymerization stress. Methods. Eleven commercially available composites and a series of experimental composites were evaluated in a mechanical testing machine to measure the maximum stress generated during placement in a confined setting. Results. A significant relationship between higher filler volume and increased polymerization stress was found among the commercial materials. Introduction of MSAA produced a 30 percent reduction in polymerization stress in an experimental composite material. Conclusions. Composites that contain lower levels of inorganic filler particles are less likely to produce high levels of polymerization stress during placement. Modifications to traditional composite chemistry can result in materials that produce lower polymerization stress levels. Clinical Implications. The polymerization stress produced by dental composite materials during light-curing is a leading reason for bond failures in adhesive restorations, resulting in postoperative sensitivity, marginal staining and recurrent caries.