Comparison Of Clinical Outcomes Of Tilted Implants And Axial Implants In All-on-4 Treatment Concept

Part 1[Objective] In this study,a systematic review was conducted to compare clinical outcomes of tilted implants and axial implants in All-on-4 treatment concept after an over 3-year follow-up period.[Methods] An electronic search was undertaken in Cochrane Library,Web of Science,Embase,Pub Med,CBM,CNKI,VIP and Wanfang until August 2019.An additional hand search of the related reviews was undertaken.The literature information was imported into Endnote software to remove the duplicated literature and conduct preliminary screening based on the tiltles and abstracts of literature.Two independent reviewers conducted study selection based on screening the full text of remaining studies which had passed the preliminary screening and determined the included studies.Then two independent reviewers extracted data of included studies based on a pre-established data extraction table and then assessed the risk of studies,and finnally conducted systematic review and meta-analysis.The primary outcome was implant failure rate and the secondary outcome was peri-implant marginal bone loss(MBL).[Results]1 632 publications were identified through the search strategy,and 12 studies which reported clinical outcomes of tilted implants and axial implants in All-on-4 concept were included.The follow-up period of all the studies were 3 years or over 3 years.A total of 1 357 patients,5 596 implants which were implanted following All-on-4 concept that consist of 2 798 tilted implants and 2 798 axial implants were included in the study.There was no significant difference in implant failure rates(RR=1.24,95% CI: [0.85,1.83],P=0.27)between tilted implants and axial implants in All-on-4 treatment concept.In terms of MBL,no significant difference was found between tilted implants and axial implants(MD=0.01,95% CI: [-0.04,0.05],P=0.81).[Conclusion] After over 3-year follow-up,no significant difference in implant failure rates and MBL was found between tilted implants and axial implants in All-on-4 treatment concept,which means that they might have similar clinical outcomes.Therefore,All-on-4 concept,in which use axial implants in combination with tilted implants to support fullarch fixed prostheses is safe and reliable.Further studies with larger sample size and longer follow-up are needed to support our findings.Part 2[Objective]To compare the 5-year clinical outcomes between tilted implants and axial implants in All-on-4 implant restoration through a retrospective study.[Methods] Patients who accepted maxillary and/or mandibular All-on-4 rehabilitation treatment in the Department of Oral Implantology,Nanjing Stomatological Hospital,Medical School of Nanjing University from October 2013 to October 2014 were followed up.After 5 years of follow-up,the differences of implant survival rate,marginal bone loss and the incidence of complications between tilted and axial implants and among tilted implants with different angles were statistically analyzed.The patient's age,sex,smoking history,periodontitis history,size of implants,direction of implants,upper/lower jaw,healing of tooth extraction at implanting site,condition of the paired jaw teeth and cantilever length in the adjacent side of implants were recorded respectively.Chi-square test was used in univariate analysis of the effects of the above factors on marginal bone loss of implants in All-on-4 concept.Then the factors with statistically significant differences were included in multivariate analysis using multiple linear regression method.[Results](1)A total of 26 patients and a total of 120 implants were involved,including 60 tilted implants and 60 axial implants.(2)The overall 5-year implant survival rate of implants in All-on-4 implant restoration was 98.33%(tilted implants 96.67%,axial implants 100%).There was no significant difference between the two groups(P=0.496).(3)After 5 years of loading,the average marginal bone loss of tilted implant was(1.16±0.98)mm,and that of axial implant was(1.11 ± 0.76)mm.There was no significant difference in marginal bone loss between the two groups(P=0.709).(4)According to the tilt angle,the tilted implants were divided into three groups(25 °~ 30 °,30 °~ 35 °,35 °~ 40 °).There were no significant differences in implant survival rate(P=0.441)and marginal bone loss(P=0.982)among the three groups.(5)Univariate analysis showed that upper/lower jaw and cantilever length were risk factors for marginal bone loss around implants in all-on-4 concept.Multivariate analysis showed that cantilever length over 10mm(P=0.001,?=0.309)was independent risk factors for marginal bone loss.(6)There was no significant difference in the incidence of biological complications between tilted and axial implants.[Conclusion] In all-on-4 concept,tilted implants had a high 5-year implant survival rate and a relatively stable marginal bone level,which was similar to that of axial implants.The change of tilt angle in the range of 25 °to 40 ° did not affect the long-term clinical effect of distal implant.In All-on-4 concept,cantilever length over 10 mm was an independent risk factor for implant marginal bone loss.Based on the results of this study,the application of distal tilted implants has satisfactory 5-year clinical outcomes.