Objective: Hydroxyaptite (HA) coating on titanium implants has been intensively investigated because it has the distinctive advantage of promoting osteogenesis. Our discharging method allowed both of bone-like HA-coating (Ca/P 1.71) and stoichiometric HA-coating (Ca/P 1.67) with thickness of 1-10mm on titanium plates by use of modified body fluid and acidic calcium phosphate solutions, respectively. This study sought to evaluate the in vivo osteoconductivity of the HA coatings. Methods: Both bone-like HA and stoichiometric HA coatings of cylindrical titanium specimens (F1.6x5.0mm) were prepared by the discharging method. Specimens without coatings were used as controls. Each specimen was implanted into a rat femur for up to 4 weeks. After excision, the specimens were stained with toluidine blue and the contact index was defined as the new bone contact to the specimen surface. Details of the bonding state between specimen surfaces and new bone were observed by scanning electron microscopy (SEM). Results were expressed as the meanąstandard deviation of six specimens (n=6). Findings were analyzed statistically by Student's t-test. Results: The contact index of both HA-coated specimens significantly increased (60%, p<0.01) compared with those of the control specimens even after 2 weeks. There was no significant difference in the contact index between each of the HA coatings (p<0.01). In the SEM study, the bone-like HA coating was observed to be completely replaced by immature bone and the titanium substrate was closely connected to the bone structure. Contrarily, the coating layer remained on the stoichiometric HA coating implants even if new bone was formulated on the coating. Conclusion: Since bone-like thin HA coating showed high osteoconductivity and bone replacement, the bone-like HA is superior than stoichiometric HA coating for use in dental implants.

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