Abstract
Chitin and Chitosan films (CCF) containing synthesized hydroxyapatite (HA) were made from five different deacetylation degrees and molecular weights of chitin and chitosan. The purpose of this study was to observe tissue reactions and effects of synthesized HA containing CCF under the periosteum of rabbit tibiae on osseous tissue. Histopathological examination was performed at 2, 4, 8, and 12 weeks after CCF implantation. At 2 weeks, in a 65% deacetylation degree CCF, granulation tissue formation with marked inflammatory cell infiltration was observed at implanted sites. In contrast, in more than 88% deacetylation degrees, their inflammatic reactions were mild, and HA components of CCF surrounded by granulation tissue or fibrous connective tissue were present. In addition, newly-formed fibrous bone or osteoids were found in such tissue. These findings were observed in all CCF,except for a 65% deacetylation degree, until 12 weeks after implantation. Cortical bones at implanted sites showed cancellous bone-like appearante caused by endochondral ossification and Haversian canal dilation, but these changes were also observed in CCF unimplanted controls. At 8 and 12 weeks, these osseous tissue changes diminished, and the tissue tended to become compact bone. The effect of different molecular weights on tissue reactions was not clarified in this study. Due to the results of this study, it was found that tissue reactions for CCF under the periosteum depended on deacetylation degrees of chitin and chitosan, and these reactions were considered to be necessary for bone substitute developments to select chitin and chitosan which are suitable for bone repair.
