Partial Implant Rehabilitations in the Posterior Regions of the Jaws Supported by Short Dental Implants (7.0 mm): A 7-Year Clinical and 5-Year Radiographical Prospective Study

Abstract

Background: Short implants have been used in the restoration of edentulous jaws in the past several years. However, some studies have suggested that short implants are less successful than standard implants. The aim of this study is to investigate the outcome of short implants placed in the posterior maxilla or mandible following one-stage or immediate-function protocols with a follow-up of 7 years (clinically) and 5 years (radiographically). Methods: This study included 127 patients rehabilitated with 217 implants measuring 7 mm and supporting 157 fixed prostheses in the posterior segments of both jaws. Final abutments were delivered at the surgery stage and were loaded after 4 months in 116 patients (199 implants). The primary outcome measure was implant survival measured through life tables. Secondary outcome measures were marginal bone loss and the incidence of biological and mechanical complications at the patient level and implant level (evaluated through descriptive statistics). Results: Twenty-four patients (18.9%) with 45 implants (20.7%) were lost to the follow-up. In total, 32 implants failed (14.8%) in 22 patients (17.3%), resulting in a cumulative survival rate at 7 years of 81.2% for 7 mm implants in the rehabilitation of the posterior regions of the maxilla and mandible. The average (standard deviation) marginal bone loss was 1.47 mm (0.99 mm) at 5 years. The incidence rate of biological complications was 12.6% and 10.6% at the patient and implant levels, respectively. The incidence rate of mechanical complications was 21.3% for patients and 16.1% for implants. A higher failure rate was registered in smokers and in implant arrangements with a sequence of three fixtures in proximity. Conclusions: Within the limitations of this study, it can be concluded that the placement of 7 mm long implants for the partial implant-supported rehabilitation of atrophic posterior jaws is possible in the long term, judging by the survival rate and stable average marginal bone loss. Nevertheless, strict case selection should be performed, especially in smokers and with implant arrangements that provide a minimum of one unit in inter-implant distance.