Long-Term Effectiveness of Extra-Short (≤ 6 mm) Dental Implants: A Systematic Review

PURPOSE This systematic review evaluated the mean survival rate and marginal bone loss (MBL) of dental implants with ≤ 6 mm in length, across a time frame of 5 years. The overall prosthetic and biologic complications were evaluated, and their survival rates obtained. In addition, the complication rates of the splinted vs nonsplinted implants were assessed. MATERIALS AND METHODS An electronic literature search in PubMed (MEDLINE) and EMBASE (OVID) and Cochrane were performed, in addition to a manual search through all periodontics and implantology-related journals, up to October 2017, to identify relevant articles. RESULTS Out of 515 potentially eligible articles, 19 investigations assessing a total of 910 extra-short (≤ 6 mm) implants were included and further evaluated. After 5 years of follow-up, a mean survival rate of 94.1% (90% in the maxilla and 96% in the mandible) and a maximum bone loss of 0.53 mm were demonstrated. Additionally, a statistically significant difference in terms of bone loss was observed between tissue-level (0.12 mm) and bone-level implants (0.36 mm) at 12 months (P < .01), but not between internal and external abutment connections (P = .17). The most commonly reported prosthetic complication was screw loosening. Finally, splinted implants showed less overall prosthetic complications (RR = 3.32; 95% CI: 1.9 to 5.7), screw loosening (RR = 15.2; 95% CI: 5.92 to 39.31), and implant failure (RR = 1.96; 95% CI: 0.8 to 4.8) than nonsplinted implants. CONCLUSION Extra-short implants are a viable treatment alternative in ridges exhibiting atrophy, demonstrating a satisfactory survival rate, as well as a low rate of prosthetic and biologic complications across a 5-year follow-up. Additionally, splinting extra-short implants is associated with fewer prosthetic complications and lower implant failure rate compared with nonsplinted implants.