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Long-term clinical evaluation of tapered multi-threaded implants: results and influences of potential risk factors.

This prospective study evaluated the long-term performance of tapered screw implants placed in patients with a variety of potentially compromising clinical variables. Sixty patients were treated with 218 implants; each case included one or more potential risk factors associated with increased rates of implant failure, peri-implant bone loss or clinical complications in the dental literature: short implants (23%), comorbid conditions (25%), maxillary implants (61%), immediate loading (88.5%), placement into extraction sockets (91%), and partial edentulism (97%). The implants were restored with a variety of prostheses. Marginal bone changes were calculated utilizing periapical radiographs taken at placement and at all subsequent appointments utilizing a standardized paralleling device and a 1-mm measurement grid. Mean clinical follow-up was 67.5 (range: 1-94) months for implants and 60 (range: 15-74) months for prostheses. Four implants failed to integrate and were immediately replaced by wide-diameter implants. Eight prostheses sustained porcelain fracture (n = 7) or cement failure (n = 1) and were replaced. No peri-implant marginal bone loss was observed for 98% of the implants; the remaining 2% exhibited 1 mm of bone loss. Cumulative survival rates were 98.2% for implants and 96.3% for prostheses after 5 years of clinical loading. Concerns that tapered implant designs may be more prone to crestal bone loss than cylinder designs are unsupported by the results of this study. Tapered implants maintained integration and marginal bone levels despite the presence of one or more potentially compromising variables.