Initial tissue response to anti-washout apatite cement in the rat palatal region: comparison with conventional...

Initial tissue response to anti-washout apatite cement (aw-AC) in the palatal region was studied. Conventional apatite cement (c-AC) was employed as a control material. Bone defects generated in the rat palatal region, where complete hemostasis is difficult to effect, were filled with both cement types and examined histologically for up to 8 weeks. At 1-week postfilling, a portion of the c-AC had washed out, resulting in slight inflammation and severe foreign-body response. The degree of foreign-body response to c-AC was reduced over time; however, foreign-body response continued to be in evidence 8 weeks after surgery. As a result, poor bone formation was observed in the case of c-AC at 8 weeks post-surgery. In contrast, aw-AC set well, maintained its shape at implantation, and caused little foreign-body response. Osteoblasts were observed at 2 weeks following surgery. Moreover, the bone defect was completely covered with new bone at 8 weeks post-surgery. This observation suggests that aw-AC may be used without complication in cases where complete hemostasis is difficult to achieve, that is, where the use of c-AC is contraindicated.