In the previous research period we developed an innovative dental composite restorative that shrinks 50 percent less than commercial methyacrylate composite restoratives. Additionally, these new composites produce at least 85 percent less polymerization stress, and have twice the fracture toughness. The invention of a three-component initiator system, and the inclusion of a polyol in the matrix resin, both of which cause the system to polymerize at clinically viable rates were key milestones. In addition, it was the discovery that the best oxirane matrices contain a cycloaliphatic and an aliphatic aromatic diepoxide. These milestones are the subjects of issued US patents. We anticipate that a first generation oxirane/polyol restorative for posterior use will be ready for clinical trails in June 2001, following further research aimed at reducing wear rates by 50 percent. Prototype composites with expanding monomers have shown further polymerization stress reduction (90 percent), but research is needed to further reduce the stress, and to bring the physical properties into ranges that are clinically viable. It is our aim to incorporate expanding monomers that have been recommended by the modeling and synthesis groups into an oxirane/polyol matrix. Our hypothesis is that expanding monomers can be combined with low shrinking oxirane/polyol resins to form a zero stress producing composite restorative with physical properties (e.g. strength, wear resistance) that are equal to or better than those of 3M Filtek Z250 Incorporation of an expanding monomer will require systematic changes to the oxirane/polyol resin matrix. Additionally, we anticipate that the biocompatibility group will recommend less mutagenic oxirane monomers for inclusion. Once the specific expanding monomers, oxirane resins, and polyol have been identified, then the principles of statistical designed experiments will be used to identify the preferred amounts of the monomer and initiator components in a composite. This is not a trivial task as there are at least seven concentration variables and many physical property requirements to be balanced, such as low polymerization stress, high strength, and low wear rates. A zero stress composite would eliminate current stress artifacts of enamel and composite cracking, and adhesive micro leakage. We will be successful when the composite strength and wear rates are equal to or better than those of 3M Filtek P60 and Z250. Subsequent generations of these innovative composites will encompass direct dental posterior use, direct anterior use, indirect dental use, dentures, and non-dental uses to replace current oxirane resins in the electronics industry.
