Studies of calcium phosphate cements for clinical applications in oral and maxillofacial surgery

Basic studies were performed in vitro and in vivo to evaluate a new type of calcium phosphate cement. This time we studied an a -tricalcium phosphate (α-TCP)/dicalcium phosphate dibasic (DCPD)/tetracalcium phosphate monoxide (TeCP) system that was developed by improving an α-TCP/DCPD system. Columns of hardened cement were used for assess the relation between compressive strength and soaking time in simulated body fluid (SBF). In addition, disks of the hardened cement were soaked in SBF and implanted in subcutaneous tissues of rats to evaluate changes in the cement by means of XRD and SEM.As compared with the former system, higher compressive strength was obtained and maintained longer, apparently because of a higher powder/liquid ratio. In XRD and SEM analyses, the cement showed HA formation after mixing, and transformation of powder components to HA as well as HA precipitation on the disks were seen both in vitro and in vivo. However, the degrees of transformation and precipitation differed between in vitro and in vivo. Histologically, the implanted disks in rats provoked the same reactions of the surrounding tissues as HA ceramics implanted in soft tissues. Significant resorption of the cement was not found histologically. However, there were signs of resorption in vivo, including SEM findings of increased surface porosity after implantation and histological evidence of multinucleate giant cells on the cement surface. Further studies of cement resorption should be performed over longer periods, in bone tissues, or both.