Hydroxyapatite-coated cylindrical implants in the posterior mandible: 10-year observations

A total of 443 hydroxyapatite-coated cylindrical implants were placed into the posterior mandibles of consenting patients from July 1985 through December 1991. Implants were placed into ridges that had sufficient bone volume. Implants were also placed in ridges with thin bone, grafted bone, or immediate extraction sites, which occasionally resulted in increased morbidity. All were followed yearly with clinical and radiographic examinations. Life table analyses were performed using SAS software. Ten-year cumulative survival and nonmorbid (based on bone loss criteria) rates were determined for the four posterior tooth locations and for all posterior locations combined. Cumulative survival for implants was 0.858 +/- 0.056 in the first premolar region, 0.833 +/- 0.041 for the second premolar region, 0.785 +/- 0.041 for the first molar region, and 0.718 +/- 0.064 for the second molar region. When all posterior mandibular locations were taken together, the cumulative survival was 0.793 +/- 0.025. Cumulative nonmorbid rates were 0.816 +/- 0.056 for the first premolar, 0.729 +/- 0.049 for the second premolar, 0.600 +/- 0.046 for the first molar, and 0.507 +/- 0.066 for the second molar. The cumulative nonmorbid rate was 0.646 +/- 0.028 for all sites combined. Comparisons between sites indicated that the second molar site had statistically more morbidity than did the other three sites. Most of the problems were identified with 8-mm-long implants, especially in the second molar location. Clinical parameters, including the presence of keratinized gingiva and a hygienic restoration, were associated with survival. Both mechanical and inflammatory compromise were found to be reasons for implant failure.