Nikolaos Pandis DDS, MS, dr. med. dent
Shorter chair time appears to be the only significant advantage to using self-ligating brackets (SLBs) over conventional brackets (CBs).
Although this is a high quality systematic review, the small number of studies of variable quality per outcome limit the strength of the evidence.
In orthodontic patients how do SLBs compare with CBs regarding efficiency (chair and treatment time), effectiveness (occlusal indices and arch dimensions), and treatment stability?
The authors searched four literature databases for studies published from 1966 to May 2009. They hand searched the references list of the retrieved articles, contacted some authors and attempted to explore the grey literature. Their inclusion criteria were clinical studies that compared SLBs with CBs regarding efficiency, effectiveness, stability; all ages and sexes; and all languages. Exclusion criteria were in vitro, ex vivo, and animal studies; studies without a comparison group; and editorials, opinions, or philosophy articles with no subjects or analytical design. Two reviewers selected studies using the stated criteria. A third investigator resolved disagreement through consensus. For studies investigating efficiency, outcomes included total treatment time, rate of mandibular incisor alignment, rate of en-masse space closure, number of visits, chair time, and bracket failure rate. For studies investigating effectiveness, outcomes included occlusal indices, arch dimensions and mandibular incisor inclinations after incisor alignment or at treatment completion. Stability outcome measures were not specified. The authors performed several meta-analyses, grouped by outcome, using a fixed-effects model if statistical heterogeneity was less than 75 percent (I2), or a random-effects model if statistical heterogeneity was greater than 75 percent (I2).
A total of 16 studies met the inclusion criteria (two randomized controlled trials, seven prospective cohorts, three retrospective cohorts and four cross-sectional studies). Sample size ranged from 134 to 1,881 participants. In all studies the subjects were mostly adolescents. All articles were published in English except one (Chinese). Of the 16 studies, the authors judged four to have low risk of bias, eight to have moderate risk of bias, and four to have high risk of bias. The included studies investigated efficiency (11 studies, meta-analysis of pooled estimates from seven studies), and effectiveness (seven studies, meta-analysis of pooled estimates from all) of SLBs as compared to CBs. No studies on stability were identified. Regarding efficiency, chair time decreased significantly with SLBs as opposed to CBs. Regarding effectiveness, there was no difference observed between the two groups, except on lower incisor inclination where the SLB showed 1.5 degrees less mandibular incisor proclination.
There is limited evidence that decreased chair time is the only advantage SLBs have over CBs in adolescent orthodontic patients (chair time is the amount of time required for opening the slides of the self-ligating brackets versus removing the conventional ligatures).
Source of Funding:
Importance and Context:
Proponents of self-ligating brackets suggest the appliance could lower required levels of force, improve treatment times, lower need for orthodontic tooth extractions, as well as reduce gingivitis, decalcification and root resorption.1-3 These benefits are both important and desirable for patients and clinician alike.
Strengths and Weaknesses of the Systematic Review:
The authors conducted a thorough review with clear inclusion/exclusion criteria. They reported their search terms and reasons for exclusion of studies, and also conducted a quality assessment of the included studies. They used two independent reviewers to examine the selected studies and performe data abstraction on prepiloted forms. The authors did not report if they blinded or calibrated their reviewers. They did not report conducting any sensitivity analyses. Because of the small number of included studies per outcome, publication bias was difficult to assess. The authors mostly adhered to PRISMA guidelines.
Strengths and Weaknesses of the Evidence:
Strengths and Weaknesses of the Evidence: The systematic review was of high quality, but the quality of the selected studies was poor. Eight studies had low risk of bias, four had moderate risk of bias, and four had high risk of bias. Only two of the included studies were RCTs. When the results were grouped for a meta-analysis, no more than three relatively small studies were considered per outcome, which weakened the evidence. Additionally, most studies included only adolescents and did not record outcomes for the all the phases of an orthodontic treatment, thus limiting generalizability. No studies on stability were identified.
Implications for Dental Practice:
Apparently, the only advantage of SLBs as compared to CBs is the reduced chair time required for opening the slides of the SLBs versus removing the conventional ligatures in CBs. However, other parameters must be considered, such as cost of the brackets and the lack of evidence for outcomes like treatment stability. There is a limited amount of literature to support the claimed benefits of SLBs. Future research should consider long term stability, periodontal effects and efficiency and effectiveness in all population groups. Clinical costs (time and expense) should also be considered.
1. Damon DH. The rationale, evolution and clinical application of the self-ligating bracket. ClinOrthod Res 1998;1:52-61.
2. Harradine NW. Self-ligating brackets and treatment efficiency. ClinOrthod Res 2001;4:220-7.
3. Damon DH. The Damon low-friction bracket: a biologically compatible straight-wire system. J ClinOrthod 1998;32:670-80.