The general goal of this research is to investigate major and radical innovations in restorative resins to enhance their clinical performance as alternatives to silver-mercury amalgams. Composite restorative materials have two major disadvantages vis-a-vis amalgam restorations; excessive polymerization shrinkage and lower wear resistance. Polymerization shrinkage values range from 1 to around 3 per cent and result in marginal gaps leading to fluid leakage. Poor relative resistance also limits the use of present materials for posterior restorations. Research is proposed on two major modifications of existing composite materials and a synthesis of new inorganic-organic copolymer. The present dimethacrylate-ceramic composites are approaching the limit on wear resistance. Further increases in the filler content will result in opacity due to random light scattering. Studies on changes in the microstructure are therefore proposed to improve properties while simulating the appearance of dental enamel. Studies are described to continue research on microballoon shrinkage reduction and unidirectional fiber reinforcement to reduce curing shrinkage and improve wear resistance and optical properties of the existing dimethacrylate systems. Another study involves the study of the alignment of ceramic filler particles by electrical fields to simulate the microstructure of mineralized tissues. The third approach is to continue research on the synthesis of a copolymer in which the inorganic phase is combined with the organic phase in a single molecular structure. This LC/silsesquioxane copolymer would eliminate the many problem including rapid wear due to matrix breakdown around filler particles common to ceramic-polymer composites with disparate physical properties. All three projects will involve considerable interaction between the investigators on creative problem solving. All three are continuing studies involving basic research that is needed to make major and radical improvements in direct polymeric restorative materials.
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