The objective of the materials testing project is to guide the evolution, refinement and fabrication of developing resin composites throughout the stages of their development. The general hypotheses is that a low shrinkage nanofilled resin composite will have mechanical and physical properties superior to a commercially available resin composite. Thus, in this project, 6 specific aims are proposed each with an underlying subsidiary hypothesis. The transverse strength and fracture toughness of the nanofiller particles in 1:1 Bis-GMA/TEGMA will be used as the screening test for specific aim 1 - It is hypothesized in specific aim 1 that the use of nanofiller particles in the resin will impart a transverse strength and fracture toughness that is equal to or greater than 80% of that of a commercially available resin composite. Specific aim 2 will screen the Bis-acrylate and -methacrylate terminated nematic liquid crystal monomers(NLCM)using the polymerization shrinkage test. In specific aim 2, it is hypothesized that the NLCM will have polymerization shrinkage that is less than 80% of the shrinkage of a clinically successful, commercially available resin composite. NLCM and nanofiller particles showing sufficient promise will be blended into various formulations of resin composite; and microstructural analyses, and mechanical and physical properties (specific aims 3, 4, and 5) will be used to characterize them. It is hypothesized in specific arms 3-5 that the nanofiller particles will be homogeneously distributed and that selected mechanical and physical properties will be superior to a commercially available resin composite. formulations showing promise will be subjected to shear bond testing using a commercially available dentin bonding agent in specific aim 6 and after dentin treatment with OP1/TGF-beta1 in specific aim 7. It is hypothesized in specific aims 6 and 7 that the shear bond strength of a prototype resin composites using a commercially available dentin bonding agent and after OP-l/TGF-beta1 treatment will be superior to the bond strength using a commercially available resin composite. It is through comprehensive tests that the ultimate formulation of the model resin composites will be selected for eventual scale up and biocompatibility evaluation.