Short Implants Versus Longer Implants In The Posterior Alveolar Region After An Observation Period Of At Least Five Years

Background: Patients with tooth loss often present periodontal disease,maxillary sinus pneumatization or disuse atrophy of the alveolar.As a result,patients who seek implant surgery are often faced with the problem of undergoing a simultaneous bone augmentation procedure.This means that the surgery would be more difficult,and patients will experience more invasive procedures and financial pressures.In recent years,the implant surface treatment technology has been used to change the topographic characteristics and surface potential energy of the implant,which has accelerated the osseointegration speed and increased the BIC area,making the application of short implants possible.However,whether the survival rate of short implants is different from that of long implants is still a controversial issue.Purpose: This meta-analysis compared clinical outcomes,including survival rate,marginal bone loss(MBL),and technical and biological complications of short implants(<7 mm)and longer implants(≥7 mm)placed in the posterior alveolar bone.Material and methods: This systematic review followed the Preferred Reporting Items for Systematic Reviews and Meta-Analyses(PRISMA)principles and was registered with PROSPERO(CRD42018112978).The authors identified eligible trials published before November 2019 by searching PubMed,EMBASE,and the Cochrane Library.Only randomized controlled trials(RCTs)were included in the study,and quality assessment was performed by using the Cochrane Collaboration Risk of Bias tool.Relevant information was extracted by using a standardized form,and a meta-analysis was performed by using a software program.Results: Nine RCTs included in this study.Survival rates of short implants(<7 mm)ranged from 86.7% to 98.5%,whereas the survival rates for longer implants(≥7 mm)were 95.1% to 100% with a follow-up from 5 to 10 years.Meta-analyses showed that short implants had a poorer survival rate than longer implants(P=0.008;RR: 0.96;95% CI: 0.94―0.99);Long implants had much more MBL than short implants(P<0.001;MD:-0.25;95% CI:-0.47―-0.04);Long implants had a lower rate of technical complications(P=0.006;RR: 1.74;95% CI: 1.17―2.59)and a higher rate of biological complications than short implants(P<0.001;RR: 0.38;95% CI: 0.27―0.54).Conclusion: Reconstruction of bone volume by maxillary sinus lift and placement of long implants may be a better option in the maxillary posterior region,nevertheless,short implants have similar survival rate to longer implants in the mandible.Employing short implants did not cause greater MBL and short implants are often accompanied by lower rates of biological complications and higher rates of technical complications.