ObjectiveThis study aimed to systematically evaluate the safety and clinical efficacy of 4 mm-extra-short implant (ESI) placement in severely atrophic posterior areas.MethodsDatabases of PubMed, Embase, Cochrane Library, Web of Science, CNKI, and Wanfang from January 1, 2010, until August 31, 2022, were searched to identify randomized controlled trials or controlled clinical trials related to ESI and standard implants (SI). An additional hand search of the references of included articles was also conducted. Meta-analyses were carried out with RevMan 5.4 software.ResultsA total of 11 studies were included, involving six randomized controlled trials and five controlled clinical trials. The meta-analyses indicated that when implants were placed in the posterior area, the implant survival rate between ESI and SI did not significantly differ [RR=1.23, 95%CI (0.66, 2.27),P=0.52]. ESI resulted in significantly stable marginal bone level [MD=-0.16, 95%CI (-0.25,-0.07),P=0.000 7] and less biological complications [RR=0.34, 95%CI (0.19, 0.62),P=0.000 4] but more mechanical complications [RR=2.89, 95%CI (1.05, 7.92),P=0.04].ConclusionBased on the limited evidence, ESI could achieve clinical outcomes similar to those of SI when the height of the posterior alveolar bone is less than 5 mm, with lower technical sensitivity and fewer postoperative clinical complications than SI. Due to insufficient evidence and limited sample size, further clinical trials are needed to verify the long-term efficacy of ESI.
