Calcium phosphates as ion-releasing fillers in restorative resin-based materials

Calcium phosphates (CaP) are the main constituents of the mineral phase in bones and teeth and, along with calcium silicates and bioactive glasses, have been extensively investigated in remineralization of enamel and dentin. When used as ion-releasing fillers in resin-based materials, they could contribute to extend the service life of adhesive restorations, remineralize caries-affected dentin or prevent caries lesions under sealants and orthodontic brackets. However, the development of resin-based bioactive materials is not straightforward because of the several compositional variables involved in ion release. Also, CaP particles do not reinforce the material; therefore, if high mechanical properties are required, the ratio between CaP particles and reinforcing fillers must be observed. Several research groups have investigated how CaP phase, particle size and content, as well as resin matrix formulation affect remineralization, ion release kinetics and mechanical properties of these materials. This review presents an overview of the main findings reported in the literature.