First Or Second Premolar Extraction Affects Proximal Movement Of First Molar-A Systematic Review

ObjectiveThis study aim to find the best evidence for the effect of the first or second premolar extraction on the proximal movemen of the first molar through a systematic review method,and to reduce the risk of bias of subsequent research by compensating for the dificiency of the exsiting evidence.MethodPubMed,Web of Science,EmBase,EBM,Cochrane library,OVID,Scopus,CNKI,Wanfang and CBM were searched until December 31,2018 with“premolar extraction”,“molar movement”and“orthodontics”.After eliminating the duplicated studies and reading abstracts,the full-text of original article that fufil the inclusion and exclusion criteria were retrieved,and the references were manually searched.High quality studies were obtained based on the inclusion and exclusion criteria.Analyse the basic characteristics of the included studies and evaluate their methodological quality,then data were extracted and Meta-analysis was performed on the included studies using Revman 5.3 software.All of the above work were done independently by two researchers and disputation were resolved through discussion or seeking third-party opinion.ResultSix studies were included,all of which were case-control studies.The methodological quality of the included studies was evaluated.The quality of two papers was Grade A,the others was Grade B.Among them,5 papers describe the effect of first or second premolar extraction on the amount of proximal movement of the maxillary first molar.Heterogeneity test showed a slight heterogeneity between the five documents(I~2=23%,I~2)<50%),so a fixed-effects model was used.The Meta-analysis revealed that the difference between the effect of the first or second premolar extraction on the amount of proximal movement of the maxillary first molar was statistically significant(MD=-0.65,95%CI[-1.07,-0.22]).Three literatures describe the effect of the first or second premolar extraction on the amount of proximal movement of the mandibular first molar.There was no heterogeneity between the three studies(I2=0%,I2<50%),so the fixed effect model was used for Meta-analysis.The results showed that the effect of removing the first or second premolar on the amount of proximal movement of the mandibular first molar was significantly different(MD=-1.36,95%CI[-1.88,-0.84]).Through sensitivity analysis,TK.Kim2005 was excluded.While The results of the new Meta-analysis showed no significant difference between the effect of removal of the first or second premolar on the amount of proximal movement of first molars.The opposite result indicates that the Meta-analysis results are unstable.ConclusionThe included studies were case-control studies,and the methodological quality was uneven.A high-methodological study played a decisive role in the overall meta-analysis.Due to insufficient high-quality research,it is not possible to draw a significant difference in the effect of the first or second premolar extraction on the amount of proximal movement of the first molar.The PICO principles should be followed when designing the original study to improve the quality of the article.