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. Keywords: dental implants, screw loosening, short implants, single crown, splinted