Long-term observation of subcutaneous tissue reaction to synthetic auditory ossicle (Bioceram) in rats.

To evaluate biocompatibility to tissue in long-term implantation, Bioceram discs made of aluminum oxide (Al2O3) were implanted subcutaneously within the interscapular region of 64 rats for six to 20 months. Histological sections stained with haematoxylin and eosin (H&E) and the surface of the implant material were observed using light microscopy. Different cell types and the thickness of fibrous capsules surrounding the implants were examined quantitatively by light microscopy. Small numbers of macrophages (2.8 +/- 0.7%) and lymphocytes (2.7 +/- 0.9%) were observed at six months after implantation, gradually decreasing to zero at 16, 18 and 20 months. Neither neutrophils nor foreign body giant cells were seen in any specimens. The thickness of fibrous capsules surrounding the implants was closely related to the shape of the implant, but there was no significant change between six and 20 months after implantation. No change in Bioceram surfaces were observed under stereoscopic microscopy from six to 20 months after implantation. The study results indicate that Bioceram is a satisfactory biocompatible material for reconstructive surgery from the viewpoint of long-term tissue response. Present results of experiments with Bioceram are also compared to previous results with Apaceram and different tissue responses of the two materials are discussed.

Subcutaneous inflammatory reaction to a synthetic auditory ossicle (Bioceram) in rats.

Cellular response and inflammatory reaction to synthetic auditory ossicle (Bioceram) made from aluminium oxide are investigated. Local inflammatory effects are important in wound healing and in determining biocompatibility of an implant, necessitating the study of biologic effects of implants, especially inflammation and fibrous capsule formation. Bioceram discs were implanted subcutaneously in the interscapular region of rats for various periods of time, ranging from 1 day to 300 days. Histological sections 6 microns thick were stained with haematoxylin and eosin. Cell types around the implants were examined quantitatively by light microscopy. Inflammatory cell reaction to Bioceram decreased rapidly within 14 days, similar to the reaction in control groups. From 30 days to 300 days after implantation, there was continuous reduction to very low levels for macrophages and lymphocytes, but fibrous connective tissue capsule around implants matured. Preliminary results suggest that Bioceram is a satisfactory biocompatible material for reconstructive surgery from the viewpoint of cellular response. We also briefly discuss the different tissue responses in light of our previous study on hydroxyapatite (Apaceram).

A subcutaneous tissue reaction in the early stage to a synthetic auditory ossicle (Bioceram) in rats.

The discs of synthetic auditory ossicle (Bioceram), which are composed of aluminium oxide (Al2O3), were implanted subcutaneously in the interscapular region of 16 rats. The implanted specimens were removed at 1, 3, 7 and 14 days after implantation. The decalcified 6 microns thick sections were stained with H.E. and cell types around the implants were counted microscopically. We found that an acute inflammatory reaction occurred at one day, in which macrophages and neutrophiles predominated, and almost disappeared at about 7 days after implantation. Fibrosis began to be observed at 3 days. During this early stage, foreign body giant cells were found in only one specimen at 3 days. These findings, in comparison with those in the controls, showed that the chemical irritation of Bioceram to the subcutaneous tissue is slight, although the physical and/or chemical irritation of Bioceram lasts continuously and induces fibrosis around the bioimplant. The results so far suggest that Bioceram seems to be a satisfactorily biocompatible material, at least within the extent of 2 weeks.