Nanocomposites with Ca and PO4 release: Effects of reinforcement, dicalcium phosphate particle size and silanization

Abstract: Objectives: Nanoparticles of dicalcium phosphate anhydrous (DCPA) were synthesized in our laboratory for the first time and incorporated into a dental resin. Our goal was to develop a mechanically strong dental composite that has Ca and PO4 ion release to combat tooth caries, and to investigate the effects of whisker reinforcement, DCPA particle size and silanization. Methods: DCPA nanoparticles and two larger DCPA particles were used with nano-silica-fused whiskers as fillers in a resin matrix. Composite mechanical properties were measured via three-point flexure, and the release of Ca and PO4 ions were measured versus time. Results: Using DCPA nanoparticles with a diameter of 112nm, the composite at a DCPA:whisker mass ratio of 1:1 had a flexural strength (mean±S.D.; n =5) of (112±17)MPa, not significantly different from (112±14)MPa of a commercial non-releasing composite; both were higher than (29±7)MPa for the composite at DCPA:whisker of 1:0 (p <0.05). The composite with DCPA particle size of 112nm released Ca to a concentration of 0.85mmol/L and PO4 of 3.48mmol/L, higher than Ca of 0.67mmol/L and PO4 of 1.11mmol/L using DCPA with 12μm particle size (p <0.05). Silanization of DCPA increased the composite strength at DCPA:whisker of 1:0 compared to that without silanization, but decreased the Ca and PO4 release (p <0.05). Increasing the DCPA particle surface area increased the Ca and PO4 release. Significance: Decreasing the DCPA particle size increased the Ca and PO4 release; whisker reinforcement increased the composite strength by two- to three-fold. The nano DCPA–whisker composites, with high strength and Ca and PO4 release, may provide the needed, unique combination of stress-bearing and caries-inhibiting capabilities. [Copyright &y& Elsevier]