Initial solubility and durability of polymeric calcium phosphate cements

对四种实验性磷酸钙牙水泥和两种商用磷酸钙牙水泥的机械强度和体外耐久性进行了评估。用x射线衍射分析研究了这些磷酸钙胶结物中羟基磷灰石的形成过程，并讨论了它们与机械强度的关系。由中、细粒磷酸四钙粉和聚甲基乙烯醚-马来酸制备的聚羟基磷灰石型聚磷酸钙水泥，其抗压强度低于用聚丙烯酸和不形成羟基磷灰石的α-磷酸三钙市产水泥制备的聚羟基磷灰石型聚磷酸钙水泥，其抗折强度高于聚羟基磷灰石型聚磷酸钙水泥。羟基磷灰石的形成似乎对应于以磷酸四钙和聚甲基乙烯醚-马来酸为基础的水泥抗压强度的降低，而以磷酸四钙和聚丙烯酸为基础的水泥，羟基磷灰石的形成与抗压强度之间没有关系。使用细磨的磷酸四钙粉制备的羟基磷灰石形成的聚合物水泥，即使在长时间浸泡在水中，也比由大尺寸磷酸四钙制成的类似水泥具有更高的强度。两种实验聚合磷酸钙胶结物的初始溶解度似乎都低于用有机酸制备的商用磷酸钙胶结物。

Mechanical strength and in vitro durability of four experimental and two commercial calcium phosphate dental cements were assessed. Hydroxyapatite formation processes in these calcium phosphate cements were also examined by means of x-ray diffraction analysis and their relationship with mechanical strength was discussed. The hydroxyapatite-forming polymeric calcium phosphate cements prepared from medium and fine tetracalcium phosphate powder and poly (methyl vinyl ether-maleic acid) showed lower compressive strength and higher flexural strength than the teracalcium phosphate cement prepared using poly (acrylic acid) and non hydroxyapatite-forming commercial α-tricalcium phosphate cements. The hydroxyapatite formation seemed to correspond to lowering in compressive strength of the cements based on tetracalcium phosphate and poly (methyl vinyl ether-maleic acid), while, in the case of the cement based on tetracalcium phosphate and poly (acrylic acid), no relationship was observed between the hydroxyapatite formation and the compressive strength. The hydroxyapatite-forming polymeric cements prepared using finely ground tetracalcium phosphate powder showed enhanced strength, even after prolonged immersion in water, compared to similar cements derived from the large sized tetracalcium phosphate. Initial solubility of both the experimental polymeric calcium phosphate cements seemed to be lower than that of the commercial calcium phosphate cements, which were prepared using organic acids.