Short (≤6 mm) compared with ≥10-mm dental implants in different clinical scenarios: A systematic review of randomized clinical trials with meta-analysis, trial sequential analysis and quality of evidence grading

Aim: To systematically identify, synthesize and critically summarize the available scientific evidence from randomized controlled trials (RCTs) regarding whether short (<= 6 mm) perform as well as long (>= 10 mm) implants regarding implant survival, marginal bone loss, and biologic and prosthetic complications in different clinical scenarios. Materials and Methods: Cochrane Collaboration's risk of bias tool and the GRADE approach were applied. Results were synthesized using random-effects meta-analyses assessed by trial sequential analyses. Results: Forty reports on 19 RCTs comprising 2214 (1097 short; 1117 long) implants were included. Moderate/high certainty/quality evidence demonstrated similar 5-year survival rates for <= 6-mm and >= 10-mm implants in non-augmented bone and full-mouth rehabilitation in either jaw, and for 6-mm implants in the maxilla instead of sinus lift. Nevertheless, the evidence for 5-year survival rates remains inconclusive or insufficient for the remaining combinations of implant lengths and clinical scenarios. They include 4-mm and 5-mm implants as alternatives to sinus lift as well as placing all implant lengths <= 6 mm instead of vertical ridge augmentation with long implants. Marginal bone level and short- and long-term biologic or prosthetic complications were similar. Conclusions: Based on moderate/high certainty/quality evidence from 5-year RCTs, implants <= 6 mm may be viable alternatives to >= 10-mm implants in either jaw in native bone and full-arch rehabilitation, and 6-mm implants may be used as an alternative to sinus lift.