Influence of Powder-Liquid Ratio on Self-Setting Apatite Cement in Bone Repair

The purpose of this study was to examine the influence of the powder-liquid ratio of self-setting hydroxyapatite cement (HAP-C) on bone repair capacity. We used 9 mongrel dogs in the experiment. The P1-P4 mandibular teeth were extracted. Three months postextraction, osseous defects (3.2×3.0mm) were created through the buccal cortical plate. Two types of HAP-C; 1) HAP-C having a powder-liquid ratio of 0.4 or 0.62) HAP -C having a porosity rate of 0% or 70%, were used to fill each of the defects, respectively. Dogs were sacrificed 2-8 weeks after surgery and block sections were prepared for histological observation. Foreign body responses were barely ovservable in the tissue around the cement in all specimens of the HAP-C group. The newly formed bone was noted to be directly in contacted with the setting cement. The implanted setting cements with a 0.4 powder -liquid ratio and 0% porosity rate remained in the osseous defects, while the cements with a 0.6 powder-liquid ratio and 70% porosity rate were replaced by newly formed bone. These results suggest that the dynamics of HAP -C in vivo are affected by its powder-liquid ratio, which may alter the porosity rate of HAP-C.