Bonding behavior of three types of hydroxyapatite with different sintering temperatures implanted in bone

The present study suggests that bonding does not vary in hydroxyapatite (HA) with different sintering temperatures implanted in bone tissue. The apparent unimportance of strict temperature regulation greatly simplifies HA processing. Three samples of HA (15 mm x 10 mm x 2 mm, abraded with 2000 alumina powder), of which sintering temperatures and microporosity were 800 degrees (45%), 1000 degrees (4.8%), and 1200 degrees (0.4%), respectively, were prepared. They were implanted into the metaphysis of tibia of mature male rabbits. Segments of the tibia containing the HA were excised and prepared for the detaching test. The failure load, when an implant detached from the bone or the bone broke, was then measured. Failure loads in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) ten weeks after implantation did not differ. Those in HA (800 degrees), HA (1000 degrees), and HA (1200 degrees) 25 weeks after implantation were 2.58 +/- 1.88 kg, 6.46 +/- 1.43 kg, and 6.50 +/- 2.71 kg, respectively. The failure load in HA (800 degrees) versus HA (1200 degrees) and that in HA (800 degrees) versus HA (1000 degrees) differed significantly (p less than 0.05). The lower failure load of HA (800 degrees) 25 weeks after implantation can be explained by its weakened mechanical strength due to high porosity. Bonding between bone tissue and three types of HA did not vary as observed by contact microradiography, Giemsa surface staining, and scanning electron microanalyzer-energy dispersive X-ray microanalyzer.