High resolution microradiography and multiple fluorochrome labeling are definitive histological methods for assessing the mechanism and timing of osseous healing, maturation, and adaptation. Two fundamental types of bone interface have been described for endosseous dental implants: (1) fibro-osseous integration ("pseudo-periodontal ligament") and (2) rigid osseous fixation ("osseointegration"). No definitive bone interface studies with modern physiological methods have been reported for fibro-osseous integration. Rigid osseous fixation has been investigated in cortical bone implantation sites. The initial healing reaction involves predominantly bone modeling at the periosteal and endosteal surfaces, i.e., a woven bone callus fills with lamellae by the process of lamellar compaction. Nonvital osseous interface and adjacent compacta are replaced by bone remodeling (turnover). As assessed with high resolution microradiography, "clinically successful" specimens had less than half of the intraosseous interface in direct contact with bone. Extrapolation from animal data suggests that endosseous implants can be provisionally loaded at about 18 weeks, but full maturation of the interface requires approximately one year.