The objective of the Biocompatibility Core is to provide complete pre-clinical biocompatibility testing for all dental resins and composites produced in the program project as well as for all new chemicals used in preparation of program project materials. Specifically the specific aims are: 1) to perform standard in vitro tests for assessment of cytotoxicity and mutagenicity; 2) to perform additional in vitro testing that will provide broader biocompatibility assessment at the level of endocrine disrupting activity and pro-inflammatory activities derived from components used in the preparation of resins and composites in the program project; 3) to perform in vivo tests in experimental animals to establish the irritation, sensitization and subchronic toxicity of materials of interest to the program project; and 4) to determine leachable components through the analysis of extracts from dental resins prepared in the program project. All biocompatibility testing will be conducted under Good Laboratory Practices (GLP) to support clinical studies of final products in humans. Standard tests will be performed as recommended for surface contacting devices and as specified in the ISO 7405 and ANSI/ADA document 41. The additional in vitro tests such as the ICSM-1-dependent inmunotoxicity testing were developed in the program project during past funding periods and now have become part of the Biocompatibilty Core activity. Standard tests will also be applied to materials that have been under-cured so as to evaluate potential misuse leading to bio-incompatibility. We anticipate testing an average of 16 specimens per year. A specimen includes new polmeric material (resin or composite), all new components and reference compounds. In vivo testing will increase during the later stages of the program project. The significance of the Biocompatibility Core activities are that individual components and the assembled dental adhesive and composite systems will have a well defined, regulatory acceptable, biocompatibility prior to clinical use assuring the safety for each patient.