Dense apatite ceramic implants inserted into fresh extraction sockets of teeth and submerged under full lower dentures may develop permucosal dehiscences because of vertical alveolar ridge resorption. In a 5-year clinical follow-up study, 16 out of 81 of such implants showed this dehiscence, offering the opportunity to study histologically the reaction of the mucosal tissue and the alveolar bone to dense apatite ceramic implants in humans. The histologic findings indicate that there is no bonding between mucosa and the permucosal part of the dense apatite ceramic implant under full lower dentures in humans. On the other hand, a very intimate bonding exists between alveolar bone and the dense apatite ceramic material.