A histomorphometric study on collagen-apatite composite as a graft material: the influence of gap size at the titanium–bone interface in animal model

The purpose of this study was to evaluate the healing process of collagen-apatite composite (CAC) at the titanium–bone interface in animal model. Small gaps (0.5 or 1.0 mm-sized wells) were prepared in the epoxy-resin block implants coated with pure titanium. The gaps were filled with CAC or demineralized freeze-dried bone (DFDB). The titanium-coated epoxy-resin block implants were inserted in the tibia of rabbit for 4 weeks or 8 weeks. The microscopic features of bony healing process in the grafted gaps were examined and analyzed. In the histomorphometric analysis, CAC group showed higher fraction of newly-formed bone than DFDB group in both 0.5 and 1.0 mm gap subgroup at 4-week specimen ( P < 0.05). In the transmission electron microscopic examinations, osteoblasts of the newly-formed bone of CAC group showed more cellular activity than that of DFDB group. From the results, it was expected that CAC had more beneficial property on early bony healing process than DFDB at the titanium–bone interface.