DESCRIPTION: Our research for the last 4 years (grant DE13169) with amorphous calcium phosphate (ACP)-based Dental composites has resulted in biocompatible composites with demineralizing ability, moderately improved mechanical strength and adhesiveness to tooth structures. Nevertheless, current ACP composites have less than optimal filler/matrix cohesion and adsorb water excessively. These factors can have adverse effects on the physicochemical and mechanical properties of these materials, and thereby limit their clinical applicability. This application outlines our research for improving the physical and antidemineralizing/ demineralizing properties of ACP composites to where they can be used in a broad variety of applications where caries control and reversal is desired. The main objectives of this application are: [1] to further study structure/composition/property relationships of ACP fillers to develop strategies that better control the dispersion of ACP in the polymer matrix, [2] investigate intracomposite filler/organic matrix interactions and composite/tooth interactions to determine the mechanisms that control mineral redeposition from these composites and [3] to extend the utility of ACP to remineralizing orthodontic adhesives. To accomplish these objectives we propose to: (a) assess the role of foreign ions/molecules in controlling the particle size, compositional and structural properties of ACP fillers while maintaining chemical stability to prevent premature intra-composite conversion to non-ion releasing crystalline apatite, (b) elucidate interfacial coupling and polymer grafting reactions as a route to enhance the interfacial strength between the ACP and the polymeric matrix, and (c) evaluate ACP-composites designed for orthodontic applications for their in vitro remineralization ability and bonding properties. The proposed research is expected to provide the new experimental evidence needed to advance our understanding of the fundamental mechanisms that govern dissolution/reprecipitation of the ACP filler and, consequently, the demineralizing ability of ACP-based Dental materials. The proposed studies should lead to the design of ACP composites for a variety of Dental applications and the formulation of a prototype orthodontic cement that is suitable for clinical evaluation.