Histologic investigation of the biologic behavior of different hydroxyapatite plasma-sprayed coatings in rabbits.

The aim of this study was to investigate bone response to and biostability of three different hydroxyapatite (HA)-coatings. Therefore, coated and uncoated titanium implants were inserted into the tibia of rabbits. Implantation times were at 3 and 12 weeks. The histological evaluation included measurement of the amount of bone apposition to the various implant surfaces. The results demonstrated at 3 and 12 weeks no marked differences in bony reaction at the cortical level to the different implant materials. However, compared with the 3-week specimens, at 12 weeks extensive maturation of the woven bone callus had occurred. In addition, all 12-week implants induced bone formation in the medullary cavity. It was also noted that all HA-coatings showed loss of coating thickness. Quantitative determination of bone contact demonstrated that all 12-week implants showed the same high amount of bone apposition.