Physicochemical evaluation of bioactive polymeric composites based on hybrid amorphous calcium phosphates

Abstract

Amorphous calcium phosphate (ACP)-filled methacrylate composites were recently found to effectively remineralize in vitro caries-like enamel lesions. Their inferior mechanical properties compared to glass-filled composites, however, limit their use as a dental restorative material. In this study, the feasibility of introducing glass-forming elements (tetraethoxysilane or zirconyl chloride) during the low-temperature synthesis of ACP was investigated. Composites based on such hybrid fillers (mass fraction, 40%) were evaluated to establish whether hybridization strengthened the composites via improved interfacial interactions with the polymer phase without compromising the release of the mineral ions. Two types of visible-light cured resins were prepared: BTHZ resin from 2, 2-bis[p-(2'-hydroxy-3'-methacryloxypropoxy)phenyl]propane (BisGMA), triethylene glycol dimethacrylate (TEGDMA), 2-hydroxyethyl methacrylate (HEMA) and zirconyl methacrylate (ZrM), and TP resin from TEGDMA and pyromellitic glycerol dimethacrylate (PMGDM). Hybridized fillers and BTHZ- and TP-based composites were characterized by the IR spectroscopy, X-ray diffraction, dissolution/transformation kinetic studies, and biaxial flexure strength (BFS) testing before and after immersion in buffered saline solutions. The feasibility of improving the BFS via hybridization, while retaining, if not enhancing the remineralizing potential was demonstrated for BTHZ-based composites. Both BFS and remineralizing ability of the TP-composites, however, deteriorated upon their exposure to an aqueous environment. Therefore, hybridized ACP-filled BTHZ composites have a potential for utilization in more demanding restorative, sealant, and adhesive applications.

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

“…Therefore, for stress-bearing restorations, it would be desirable to use a composite with a DCPA:whisker ratio near 1:1 using unsilanized DCPA nano-particles, which produced a Ca concentration of 0.35 mmol/L and PO 4 of 0.99 mmol/L (at 56 d). These concentrations matched or exceeded the reported Ca and PO 4 concentrations measured using a similar method for previous calcium phosphate composites known to remineralize enamel and dentin lesions in vitro [18][19][20][21]. For example, amorphous calcium phosphate (ACP) composites yielded a Ca concentration of 0.3 mmol/L to 1.0 mmol/L, and a PO 4 concentration of 0.2 mmol/L to 0.7 mmol/L (Figs.…”

“…Hence there is a wide range of solution conditions when the precipitation of hydroxyapatite occurs spontaneously. Indeed, several bioactive composites have been developed that release calcium and phosphate ions in the presence of an aqueous solution, which then precipitate to form hydroxyapatite [18][19][20][21]. The calcium ions are conveniently referred to as Ca, and the phosphate ions as PO 4 , following previous studies [20,21].…”

“…For example, a calcium phosphate composite had a flexural strength of about half of the strength of the unfilled resin [19]. Such low strengths were recognized as being "inadequate to make these composites acceptable as bulk restoratives" [20].…”

Calcium orthophosphate-based biocomposites and hybrid biomaterials

“…Various ACP-based biocomposites for dental applications were developed [415][416][417][418]. Besides, several ACPbased formulations were investigated as potential biocomposites for bone grafting [349,[419][420][421].…”

“…Therefore, polymers with functional groups pendant to the polymer backbone, which can act as sites for bridging to calcium orthophosphates, are more promising in this respect [49]. Besides, the surface of calcium orthophosphates might be modified as well [116,416,417,552,914,915]. In order to improve the situation, various supplementary reagents are applied.…”