The research on dental materials that is described in this report is a part of a larger total effort that is carried out in collaboration with the American Dental Association Health Foundation. The U. S. Army and Navy Medical R&D Command and the School of Dentistry, Georgetown University are also part of this collaborative effort through support funding and/or assignment of research personnel.While the bulk of the research progress in this report represents only the efforts of NBS staff supported under the Interagency Agreement with NIDR, there will of necessity be a degree of contribution that originates through the intentionally strong interaction among all persons participating in this collaborative dental program.The objective is to effect improved dental health through development of new knowledge and better understanding of the mechanical, chemical, and physical properties of restorative and caries-preventive materials and the mechanisms by which clinical performance is governed.A wide variety of techniques has been brought to bear to generate approaches to new and improved adhesive restorative dental materials These include: syntheses of components to improve current composite restorative materials and pit and fissure sealants and development of techniques that can be used to examine the extent of the polymerization reaction in dental resins and components, investigation of new approaches to bonding restorations to tooth surfaces, determination of the mechanisms by which composite systems wear and degrade in clinical use coupled with production of accelerated laboratory wear test data, and development of characterization methods and data for analyzing the compatibility of dental porcelains for base metal alloys.

New polymeric formulations designed to reduce curing shrinkage, residual unsaturation and hydrophi 1 icity in dental composite restorations have been developed and evaluated. To reduce polymerization shrinkage emphasis has been placed on high molecular weight bulky monomers such as blends of BIS-GMA and diurea dimethacrylate types. While typically moderate to fast-acting accelerators such as bis(N ,N-2-hydroxypropyl )ptoluidine or p -tert-butyl -N ,N-dimethylani 1 ine could not be used with such formulations, substitution of slower acting accelerators such as ethyl -4-dimethyl ami nobenzoate or ascorbyl palmitate yielded formulations that set in clinically acceptable times.Powder/liquid, paste/paste or single paste/visible light cured formulations produced composites with