Structure of the bone interface to dental implants in vivo.

Dental implant materials can develop different kinds of interfaces when used for bone or tooth substitution. This paper describes the tissues and the tissue reactions of the interface created in the implantation bed between bone tissue and implants made of dense sintered hydroxylapatite. Healing was clinically and histologically evaluated during a six-month to five-year period. The light microscopic results show extensive bone apposition on the osseous sides of loaded implant cylinders and also on subperiosteally placed granules of dense hydroxylapatite. The presence of the loaded implant did not disturb the normal bone physiology. Bone turnover also included the bone tissue toward the implant surface. At the ultrastructural level, an amorphous collagen-free zone of about 200 nm was frequently observed which was separated from the surrounding mineralized extracellular matrix by a thin, electron-dense layer of about 20-100 A. Contact microradiographs showed an intimate bond to bone. The bone growth extending up the implant cylinder was always accompanied with an embedding of collagen fibers and the presence of a well-developed and complete new gingival attachment apparatus. This was confirmed by scanning electron microscopy. However, any inflammatory reactions in the transmucosal area were accompanied with concomitant bone resorption and loss of bone support.