Clinical Efficacy Of Extra-short Implant (4 Mm) Placed In Posterior Areas: A Meta-analysis

Objective: To systematically review the implant survival rate and marginal bone loss as well as complications of 4 mm extra-short dental implants compared with standard implants in order to evaluate the safety and clinical efficacy of 4 mm extrashort implant placement in severely atrophic posterior areas.Methods: Databases of Pub Med,Embase,Cochrane Library,Web of Science,CNKI and Wanfang from January 1st 2010 until August 31 st 2022 were searched to identify randomized controlled trial or controlled clinical trial related to ESI and standard implants(SI).The subject words "extra-short implants,implant survival rate,marginal bone loss,complications" were adopted to search literature on the above databases.An additional hand search of the references of included articles was also conducted.Two independent reviewers independently screened literature,extracted data,and evaluated the bias risk of included studies.If there were any difference,it shall be settled through negotiation.If no agreement can be reached,the third researcher carried out further discussion and decision.After screening and methodological evaluation,meta-analyses were carried out with Review Manager Version 5.4 software.The difference of the implant survival rate、marginal bone loss and complications between the ESI and SI will be evaluated in the effect size expressed as risk ratio(RR)or mean difference(MD).The inspection level of meta-analysis was P=0.05.Results: A total of 11 studies were included,involving 6 randomized controlled trials and 5 controlled clinical trials.A total of 560 patients with 1007 implants were included and the follow-up period was 1-5 years.Meta-analyses indicated that when implants were placed in the posterior area,there was no significant difference in implant survival rate between ESI and SI [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=0.0007],and less biological complications [RR=0.34,95%CI(0.19,0.62),P=0.0004],but more mechanical complications [RR=2.89,95%CI(1.05,7.92),P=0.04].Conclusions: Based on the limited evidence,ESI can achieve similar outcomes comparable to SI when the height of posterior alveolar bone is less than 5 mm,with lower technical sensitivity and fewer postoperative clinical complications.Due to insufficient evidence and limited sample size,further clinical trials are needed to verify the long-term efficacy of ESI.