Fixed and Removable Full-Arch Restorations Supported by Short (≤ 8 mm) Dental Implants in the Mandible: A Systematic Review and Meta-Analysis

Purpose: To evaluate, through a systematic review of the literature, the published data regarding marginal bone loss, implant failure proportion, biologic and prosthetic complications, and risk factors associated with short (≤ 8 mm) implants supporting fixed or removable full-arch restorations in the edentulous mandible. Materials and Methods: Two reviewers performed a search of five databases, with handsearching through the reference lists and gray literature. Controlled clinical trials and prospective cohort studies were selected in a two-phase process. The data were independently gathered by the same two reviewers. Quality assessment of the studies was done using the Cochrane Handbook for Systematic Reviews of Interventions for Randomized Clinical Trials and the Newcastle-Ottawa Scale for Prospective Cohort Studies. Marginal bone loss and implant failure proportion were meta-analyzed using random and fixed-effects models, respectively, with 95% confidence intervals. A descriptive analysis was performed of the prevalence of biologic and prosthetic complications. Meta-regression analysis was run as fixed-effect models for risk factors. Results: Six studies met the eligibility criteria and had data extracted. A total of 291 short implants (lengths 5 to 8 mm) were placed in 122 patients (82 women; mean age, 64.7 ± 10.8 years) supporting 23 fixed and 99 removable full-arch restorations. The pooled marginal bone loss overall was 0.12 mm (0.07 to 0.17 mm). Marginal bone loss for fixed full-arch restorations was 0.11 mm (0.01 to 0.21 mm) and for removable full-arch restorations was 0.14 mm (0.07 to 0.21 mm). The pooled overall implant failure proportion was 2.0% (1.0% to 5.0%) for the studies. Implant failure proportion for fixed and removable restorations was 2.0% with confidence intervals of 0.0% to 9% and 0.0% to 6%, respectively. The prevalence of prosthetic complications was 34.5% for fixed restorations and 2.6% for removable restorations. No biologic complications were found for fixed restorations, while 13.1% of removable restorations did have biologic complications. Risk factors did not demonstrate statistical differences regarding implant failure proportion and marginal bone loss. All included studies demonstrated a high methodologic quality. Conclusion: Findings from this systematic review and meta-analysis suggest that full-arch restorations supported by short implants in atrophic edentulous mandibles might be a viable treatment option, presenting minimal marginal bone loss and implant failure in the short term. However, further well-performed prospective clinical trials with long-term observation are needed. Keywords: edentulous patients, meta-analysis, short implants, systematic review