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

ABSTRACT

OBJECTIVE: 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 (DCPDBG) and DCPD particle sizes. METHODS: Ten resin-based composites (50 vol% inorganic fraction) were prepared using BG (0.4 µm) and DCPD particles (12 µm, 3 µm or mixture) with DCPDBG of 13, 11 or 31. 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 24 h. 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). RESULTS: %T was significantly reduced in composites with milled, compared to pristine DCPD (p < 0.001). ΔE > 3.3 were observed with DCPDBG of 11 and 31 formulated with milled DCPD (p < 0.001). DC increased at 11 and 31 DCPDBG (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 DCPDBG (p < 0.001). Reductions in FM were observed with milled DCPD (p < 0.001). WS/SL increased with DCPDBG (p < 0.001). At 3DCPD 1BG, using small DCPD particles led to a 35 % increase in calcium release (p < 0.001). SIGNIFICANCE: 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.