SYNOPSIS
In the present study, bone regeneration using gelatin/calcium phosphate (CaP) paste with different degradation rates of gelatin was evaluated after implantation into the cortical bone of rabbit tibiae with a bone healing process. Three types of gelatin: gelatin SL (smaller size and low degree of cross-linking), gelatin LL (larger size and low degree of cross-linking), and gelatin LH (larger size and higher de-gree of cross-linking) were prepared. A powder mixture of each gelatin and CaP was mixed with a liquid. The mixed paste was filled into cortical bone defects of rabbit tibia. As a control, CaP paste without gelatin was used. After 12 weeks of implantation, bone response was evaluated by preparing non-decalcified thin sections. In the control, new bone formation was recognized but much amount of remaining CaP particles was clearly observed inside the newly formed bone besides in the bone defect area. For gelatin SL/CaP and LL/CaP, more than half of the space of the bone defect was filled with new bone. Degradation residues of gelatin were recognized in the bone marrow side of the bone defect and small amounts of CaP particles were remained in the gelatin residue. For gelatin LL/CaP, new bone formation was also observed, but residual gelatin degradation was not clearly identified, and greater amounts of remaining CaP particles was recognized. In conclusion, it revealed that present gelatin/CaP pastes promoted new bone formation. The present gelatin/CaP paste should be useful as a bone regenerative material.

Key words: gelatin, calcium phosphate paste, degree of cross-linking, cortical bone regeneration