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

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 112 nm released Ca to a concentration of 0.85 mmol/L and PO4 of 3.48 mmol/L, higher than Ca of 0.67 mmol/L and PO4 of 1.11 mmol/L using DCPA with 12 mu m 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. (c) 2007 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.