In vitro Cytotoxicity of Amorphous Calcium Phosphate Composites

Abstract

Calcium phosphate-based biomaterials are being increasingly used as bone substitutes in dentistry and in reconstructive and orthopedic applications because of their good biocompatibility, osteoconductivity and/or bone-bonding properties. In this study, the in vitro cytotoxicity of the amorphous calcium phosphate (ACP) filler, the copolymer matrix derived from the polymerization of a resin system and the corresponding ACP composite was analyzed utilizing cell culture techniques. The photo cured polymer was derived from an activated resin comprised of an ethoxylated bisphenol A dimethacrylate, urethane dimethacrylate, triethylene glycol dimethacrylate, and 2-hydroxyethyl methacrylate. The resin was admixed with a zirconia-ACP filler to prepare the composite. Specimens were extracted in media overnight and then MC3T3-E1 osteoblast-like cells were cultured in the extracts for 3 days. Cytoxicity was evaluated by phase contrast microscopy and an enzymatic assay for mitochondrial dehydrogenase activity (Wst-1). Cellular response to the experimental ACP composite was compared to the cellular response of commercially available light-cure orthodontic adhesive. In addition to the cytotoxicity testing the ion release profiles of ACP composites was determined. Furthermore, a degree of vinyl conversion (DVC) attained in the experimental composite and in the commercial control was compared. No adverse response regarding cell morphology and/or viability was observed with ACP composites compared to the unfilled copolymers or to the commercial adhesives. Sustained release of potentially remineralizing calcium and phosphate ions and favorable DVC of these composites confirms their value in a variety of dental and possibly orthopedic applications where anti-demineralizing/remineralizing efficacy is the primary goal.