Histologic evaluation of a threaded hydroxyapatite-coated root-form implant located at a dehisced maxillary site and retrieved from a human subject: a clinical report.

This clinical report describes the microscopic analysis of a threaded hydroxyapatite-coated root-form implant retrieved from an 89-year-old subject after 10 months of service. The implant was never loaded and was removed because it was nonrestorable. Clinically, the buccal area of the implant was covered by soft tissue, whereas the palatal side was covered by bone. Light microscopic evaluation revealed tight contact between hydroxyapatite and bone with no sign of coating dissolution. Osteocytes were present, and Haversian canals were in close proximity to the implant surface. The buccal side of the implant demonstrated mild to moderate inflammatory infiltrate and signs of hydroxyapatite coating dissolution. These observations suggest that hydroxyapatite coatings can resist degradation in contact with bone but may be more prone to dissolution in contact with soft tissue.