Examination of human bone surrounded by a dense hydroxyapatite dental implant after long-term use

A high-density hydroxyapatite (D-HAP) ceramic dental implant that had functioned for more than 5 years was studied, using light and electron transmission microscopy, after it was retrieved from a human mandible. The D-HAP implant had come in contact with thick bone trabeculae; in the nontrabecular area, a thick bone addition was formed on the implant. The lamellar arrangement of the added bone was basically parallel to the implant's surface and continuously connected with the lamellar surface layer of the trabeculae at the added bone-trabeculae connection. Also, bone remodeling around the implant had occurred, especially in the area contacting the thickened trabeculae, wherein remodeling units were formed parallel to the implant surface. Moreover, positive results of chemical bonding existed and were recognized between the D-HAP and the bone. No structural changes were observed in the D-HAP ceramics. From this study, the characteristics of biological affinity, functional adaptability, and material stability suggested that D-HAP is a suitable material for dental implants.