Comparison of anchorage loss between conventional and self-ligating brackets during canine retraction – A systematic review and meta-analysis

Abstract

Anchorage is defined as the resistance to unwanted tooth movement. In orthodontics, loss of anchorage can be detrimental to treatment. The proponents of orthodontic self-ligating brackets (SLB) advocate the use of extremely light forces thereby reducing anchorage burden. Therefore, the aim of this study was to compare anchorage loss during canine retraction between conventional brackets (CB) and self-ligating brackets. An electronic search was conducted on the Cochrane database, Scopus, Web of Science, PubMed, Dental & Oral Science and CINAHL, along with handsearching Google Scholar and clinicaltrials.gov. Randomized or non-randomized clinical trials published in the English language on human subjects were included. Orthodontic patients undergoing canine retraction after premolar extraction bonded with self-ligating brackets as the intervention and conventional brackets as the control group in a split mouth design were included. Primary outcome studied was anchorage loss; secondary outcomes were retraction velocity and total amount of canine retraction. Two researchers carried out data extraction and study selection independently. The risk of bias was calculated using the Cochrane's Risk of Bias Assessment tool. The RevMan software was used for quantitative synthesis of data. Effect estimate of the primary and secondary outcomes was expressed using weighted mean difference and 95% confidence intervals (CIs). Heterogeneity of the studies was evaluated using the Cochrane's test for heterogeneity (I2 Test); subgroup and sensitivity analyses were performed to investigate sources of heterogeneity among the studies. Results of the literature search across all databases yielded 10,439 hits, out of which five studies were included in the qualitative synthesis that met the inclusion criteria. Four studies were randomized control trials (RCTs) where as one was a non-randomized control trial, with 100 subjects included in this systematic review. All studies used a split mouth design. Of the five studies included, only one reported significant differences between CB and SLB for anchorage loss, retraction velocity and total amount of canine retraction (P-value≤0.001). Four studies were included in the meta-analysis, which showed no difference in the amount of anchorage between self-ligating and conventional brackets (weighted mean difference-0.22; 95% CI [-0.82, 0.38]; P=0.48). Multiple subgroup analyses further revealed there were no significant differences between the intervention and control groups for all outcomes studied. This systematic review and meta-analysis found insufficient evidence to suggest a significant difference in anchorage loss between the CB and SLB groups. The scarcity of current evidence dictates that further studies are needed to canonically establish the clinical superiority of one over the other. PROSPERO 2019 CRD42019133217.