Efficiency of self-ligating vs conventional braces: systematic review and meta-analysis
Objectives The purpose of this section is to review the clinically significant effects of self-ligating brackets on orthodontic treatment with respect to the quality of available scientific evidence, and, finally, clarify if and which is the advantage of these different brackets in terms of overall treatment time and number of visits.
Matherials and methods A systematic analysis was made using the Pubmed Database and manual search in the references of articles identified; our search for relevant articles took place between September 2014 and January 2017 using the following terms: Self-ligating* AND conventional AND bracket* AND conventional AND bracket* AND treatment time AND conventional AND bracket* AND time.
In addition, we checked the indices of American Journal of Orthodontics and Dentofacial Orthopedics, European Journal of Orthodontics, Journal of Orofacial Orthopedics, Orthodontics and Craniofacial Research, and The Angle Orthodontist. This review’s pre-defined protocol was based on the Cochrane guidelines.
Five key methodological criteria were assessed: sample size calculation, random sequence generation, allocation concealment, reporting of dropouts, and blinding of measurement assessment. An overall assessment of risk of bias (high, medium, low) was undertaken for each included trial using the Cochrane collaboration criteria.
To be included in the review, trials had to meet the following selection criteria.
- Study design: randomized and controlled clinical trials.
- Participants: patients with full arch, fixed orthodontic appliance(s) treated with self-ligating brackets (SLBs) or conventional brackets (CBs).
- Interventions: fixed appliance orthodontic treatment involving SLBs or CBs.
- Outcome measures: the outcome measures were overall treatment time and number of appointments, related to both SLB and CB systems.
The meta-analysis was calculated using the software MetaXL 2.2, specifying standardized mean differences (SMD) and 95% confidence intervals (CI) in a random effects model.
A total of 43 citations were identified electronically and 9 more manually, after exclusion procedure, only three studies met the criteria and were included in the systematic review and in the meta-analysis (Fleming, DiBiase, Johansson).
Results and conclusions Overall treatment time: even if the total duration of the treatment was higher in the self ligating brackets group than in that of the conventional brackets in all the three studies, in none of the studies statistical significance was reached.
Therefore, across studies, heterogeneity did not emerge in the presence of the effect of the type of treatment on the total duration.
Number of appointment: in the first and third studies (Fleming, Johansson), the number of appointments resulted greater in the self-ligating group than in that of conventional brackets group, while in the second study the conventional brackets group shows a greater number of appointments. It can be noted however that none of the three primary studies reached significance.
Clinical significance Results from our meta-analysis revealed weak and statistically not significant overall effects that failed to substantiate major advantages of self-ligating brackets over conventional brackets.
We realized that the small number of included trials carries its own limitations in clarifying the differences between conventional and self-ligating brackets.
The application of less strict criteria would have raised the probability of bias in the meta-analysis.
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