Effect of the monomer and filler systems on the remineralizing potential of bioactive dental composites based on amorphous calcium phosphate

Amorphous calcium phosphate (ACP), because of its high solubility and its rapid transformation to hydroxyapatite (HAP) in aqueous environments, has been utilized as the filler phase in the preparation of bioactive polymer-based composites that have remineralization potential. The goal of this study was to evaluate the effects of chemical structure and compositional variations of seven photopolymerizable matrix monomer systems on the long-term release of calcium and phosphate ions, i.e., their remineralizing potential, when used with three types of ACP filler systems. unhybridized ACP (u-ACP), silica-hybridized ACP (S ACP), and zirconia-hybridized ACP (Zr-ACP) composites. The monomer systems evaluated were: 2,2-bis[p-(2 ' -hydroxy-3 ' -methacryloxypropoxy)- phenyl]-propane (Bis-GMA)/triethyleneglycol dimethacrylate (TEGDMA) [BT resin], Bis-GMA/TEGDMA/2-hydroxyethyl methacrylate (HEMA) [BTH resin], Bis-GMA/TEGDMA/HEMA/zirconyl methacrylate (ZrMA) [BTHZ resin], TEGDMA/pyromellitic glycerol dimethacrylate (PMGDMA) [TP resin], a urethane dimethacrylate, [U] and two HEMA-modfied U resins with the mass fraction of 6.6% and 13.2% HEMA, ([U66H] and [U132H], respectively). All the visible light polymerizable composites consisted of 60% resin and 40% ACP filler on a mass fraction basis. It was shown that ion release from the immersed composites was affected by both the chemical structure and composition of the monomer system as well as the type of filler system. whereas BT, U and U66H resins formulated with u- ACP gave low to moderate levels of ion release, the resins with elevated amounts of HEMA (BTH, BTHZ and U132H) gave high and sustainable release of mineral ions. The remineralizing capacity of BT, U, U66H and U132H composites generally increased when hybridized fillers were employed instead of u-ACP. Utilization of hybrid ACPs had, however, no effect on ion release from BTHZ composites. The TP composites initially gave high ion release, but it was not sustainable because of significant Ca-binding by the matrix due to the high content of carboxylic acid groups derived fi om the PMGDMA comonomer. Copyright (C) 2001 John Wiley & Sons, Ltd.