Osseointegrated Titanium Implants:Requirements for Ensuring a Long-Lasting, Direct Bone-to-Implant Anchorage in Man

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Abstract
A total of 2895 threaded cylindrical T implants were inserted into the mandible or the maxilla and 124 similar implants were installed in the tibial, temporal or iliac bones in man for various bone restorative procedures. The Ti screws were implanted without the use of cement, using a meticulous technique aiming at osseointegration - a direct contact between living bone and implant. Stable and integrated screw [38] were removed for various reasons from 18 patients. The interface zone between bone and implant was investigated using X-rays, SEM [scanning electron microscopy], TEM [transmission electron microscopy] and histology. SEM study showed a very close spatial relationship between Ti and bone. The pattern of the anchorage of collagen filaments to Ti appeared to be similar to that of Sharpey''s fibers to bone. No wear products were seen in the bone or soft tissues in spite of implant loading times up to 90 mo. Soft tissues were also closely adhered to the Ti implant, thereby forming a biological seal, preventing microorganism infiltration along the implant. Implants in many cases were allowed to permanently penetrate the gingiva and skin. This caused no adverse tissue effects. An intact bone-implant interface was analyzed by TEM, revealing a direct bone-to-implant interface contact also at the EM level, thereby suggesting the possibility of a direct chemical bonding between bone and Ti. Osseointegration is a reliable type of cement-free-bone anchorage for permanent prosthetic tissue substitutes. At present, this technique is being tried in clinical joint reconstruction. To achieve and maintain such a direct contact between living bone and implant, threaded, unalloyed Ti screws of defined finish and geometry were inserted using a delicate surgical technique and were allowed to heal in situ, without loading, for at least 3-4 mo.

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