Porous titanium endosseous dental implants in Rhesus monkeys: microradiography and histological evaluation

Artificial tooth roots with porous surface coatings were fabricated by sintering spherical powder of titanium alloy to solid cylindrical cores. The tooth roots were implanted subgingivally in healed mandibular premolar extraction sites of fifteen Rhesus monkeys. Supracrestal abutments were screwed into pretapped holes in the superior aspect of the primary subgingival stage four to eight weeks after implantation of the root. Clinical evaluations were performed monthly. Ten animals were sacrificed for histological evaluation of the functioning free standing implants. Of twenty-nine implants placed, three were lost and four were rated failures on the basis of histological evaluation. Postmortem evaluations revealed bone growth into the porous surface coating of the primary stage of all the implants. The most characteristic features which could be used to describe differences in the implant histology were the buccal and lingual crestal bone heights measured in relation to the root porosity. Twelve of sixteen implants had crestal bone heights within one millimeter of the superior aspect of the root. Four other implants displayed excessive bone recession, revealing as much as one half of the root porosity supracrestally. The four implant failures could be related to unfavorable features of recipient bone sites. The results demonstrate that the bone growth into the porous surface coatings of artificial tooth roots is an efficacious method of dental implant fixation.