Histological behaviour of zirconia implants: An experiment in rats

New biomaterials including surface modifications should undergo in vitro and in vivo evaluation before clinical trials. The objective of our in vivo study was to evaluate the biocompatibility of one of the newly fabricated zirconia implant surfaces, called “mds”. For this purpose, the osseointegration of these implants was analyzed after implantation in surgically created defects in the cranium of adult male rats. After a healing period of 28 and 56 days, respectively, bone tissue specimens containing the implants were processed and histologically analyzed. For this purpose, sections were stained with haematoxylin/eosin and Masson Goldner trichrome. No signs of cellular inflammatory infiltrate were found in any of the animals. After 28 days, slices showed pronounced development of blood vessels and bone regeneration. After 56 days of healing, direct bridging of the bone defects was detectable with distinctly visible kit lines. There were cell rich areas of connective tissue/bone marrow between zirconia discs and bearing bone. Histomorphometric analysis presented a regenerated bone mean value of 36.3% after 28 days of healing. After 56 days of healing, a 1.6 fold increased bone mean value was observed (58.2%). Using the same analysis, 1% and 39.9% of bone-implant-contact was visible after both healing periods, respectively. On average, connective tissue/marrow spaces occupied 99% of implant-contact-area after 28 days of healing. This area was reduced to 60.1% after 56 days. Within the limits of the animal investigation presented, it was concluded that the tested surface modification of zirconia implants were biocompatible and osseoconductive.