PHYSICAL AND CHEMICAL-PROPERTIES OF RESIN-REINFORCED CALCIUM-PHOSPHATE CEMENTS

Objectives. The purpose of this study was to improve the handling and physical properties of a self-setting, water-based calcium phosphate cement by combining it with polymerizable resins and to study the setting reactions involved. Methods. Dual-cured composite cements were prepared from a calcium phosphate cement powder and dental monomers that contain carboxylated hydrophilic resins or resin/water mixtures. The setting reaction of the calcium phosphate cement in the presence of the resins was evaluated by pH measurements, infrared spectroscopy, diametral tensile strength, x-ray diffraction analysis, and scanning electron microscopy. Results. Carboxylated resins were chosen because they can form ionic bonds to the mineral filler, which was confirmed by appearance of an infrared absorbance peak at 1552 cm(-1) within 24 h after mixing due to the formation of a carboxylate salt. Hydroxyapatite did not develop in composites prepared from resin and calcium phosphate cement. However, composites from calcium phosphate cement, resin and water showed approximately 40% hydroxyapatite. The resulting composite cements have moderately high DTS of 14-15 MPa and high pH. Significance. Hydrophilic acidic resins allows mixing with water and/or allow rapid diffusion of water into the resinous cement so that the dissolution and reprecipitation processes required for the conversion of the calcium phosphate components to hydroxyapatite can occur. The characteristics of the resulting composite cements suggest that the materials may be useful in pulp capping and/or cavity lining.