Improvement in zirconia osseointegration by means of a biological glass coating: An in vitro and in vivo investigation

The biocompatibility and osseointegration of zir- conia (ZrO2), either coated with RKKP bioglaze or un- coated, were evaluated in vitro and in vivo. The in vitro test was performed in human osteoblasts, whereas maximal sen- sitization was performed in 23 Dunkin Hurtley guinea pigs. RKKP bioglaze-coated and uncoated (controls) ZrO2 cylin- ders were implanted in the distal femoral epiphyses of 14 Sprague-Dawley rats under general anesthesia, and animals were sacrificed at 30 and 60 days. Lactate dehydrogenase, alkaline phosphatase, and Thiazolyl Blue (MTT) were tested in vitro. A graded score was used for evaluating the results of the sensitization test. Histomorphometry and microhard- ness testing were performed to quantify the osseointegration rate, as well as bone quality around the implants. Neither in vitro cytotoxicity nor sensitization were observed. Histomor- phometry demonstrated that at 30 days, the affinity index was significantly higher in coated implants than in uncoated ones (p < 0.05); at 60 days, the behavior of coated implants was better than that of uncoated ones, but differences were not significant. Significant increases in bone microhardness were found at 1000 m from the interface area for both uncoated (p < 0.0005) and RKKP bioglaze-coated (p < 0.0005) ZrO2, and also within 200 m from the interface (p = 0.014) but only for coated ZrO2. These results suggest that RKKP bioglaze-coated ZrO2 permits biocompatible devices with improved osseointegration properties to be manufac- tured. © 2002 Wiley Periodicals, Inc. J Biomed Mater Res 61: 282-289, 2002