Effect of calcium orthophosphate particle size and CaP:glass ratio on optical, mechanical and physicochemical characteristics of experimental composites.

Abstract

Evaluate light transmittance (%T), color change (ΔE), degree of conversion (DC), bottom-to-top Knoop microhardness (KHN), flexural strength (BFS) and modulus (FM), water sorption/solubility (WS/SL) and calcium release of resin composites containing different dicalcium phosphate dihydrate (DCPD)-to-barium glass ratios (DCPD:BG) and DCPD particle sizes. Ten resin-based composites (50vol% inorganic fraction) were prepared using BG (0.4µm) and DCPD particles (12µm, 3µm or mixture) with DCPD:BG of 1:3, 1:1 or 3:1. A composite without DCPD was used as a control. DC, KHN, %T and ΔE were determined in 2-mm thick specimens. BFS and FM were determined after 24h. WS/SL was determined after 7 d. Calcium release was determined by coupled plasma optical emission spectroscopy. Data were analyzed by ANOVA/Tukey test (alpha: 0.05). %T was significantly reduced in composites with milled, compared to pristine DCPD (p<0.001). ΔE>3.3 were observed with DCPD:BG of 1:1 and 3:1 formulated with milled DCPD (p<0.001). DC increased at 1:1 and 3:1 DCPD:BG (p<0.001). All composites presented bottom-to-top KHN of at least 0.8. BFS was not affected by DCPD size but was strongly dependent on DCPD:BG (p<0.001). Reductions in FM were observed with milled DCPD (p<0.001). WS/SL increased with DCPD:BG (p<0.001). At 3DCPD: 1BG, using small DCPD particles led to a 35% increase in calcium release (p<0.001). A trade-off between strength and Ca2+ release was observed. In spite of its low strength, the formulation containing 3 DCPD: 1 glass and milled DCPD particles is preferred due to its superior Ca2+ release.