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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° (45%), 1000° (4.8%), and 1200° (0.4%), respectively, were prepared. They were implanted into the me-taphysis 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°), HA (1000°), and HA (1200°) ten weeks after implantation did not differ. Those in HA (800°), HA (1000°), and HA (1200°) 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°) versus HA (1200°) and that in HA (800°) versus HA (1000°) differed significantly (p < 0.05). The lower failure load of HA (800°) 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.
Kitsugi et al. (Thu,) studied this question.