We read with great interest the systematic review of the Fränkel appliance in the August 2014 issue of the Journal (Yang X, Li C, Bai D, Su N, Chen T, Xu Y, et al. Treatment effectiveness of Fränkel function regulator on the Class III malocclusion: A systematic review and meta-analysis. Am J Orthod Dentofacial Orthop 2014;146:143-54). This review challenged the common presumption that the long-used Fränkel function regulator was effective in managing Class III malocclusions. However, we believe that there was a mistake in the inclusion of the trials. We noticed that the number of participants in a trial conducted by Waheed-Ul-Hameed was too small (only 10 in each group). Having too few participants would certainly increase the probability of type II error (risk of false-negative). It seemed that there lacked sample-size estimation in the trial conducted by Waheed-Ul-Hameed. Yet the authors assessed this trial as “high quality” in the Newcastle-Ottawa scale and included it in the meta-analysis. As a result, except for the comparison of “overjet changes,” which could not serve as the primary outcome, there was a wide confidence interval in every other pooled analysis. The lack of statistical accuracy of this trial due to limited participants would influence the overall pooled result. Thus, this trial should not be included in the meta-analysis, or subgroup analysis is needed excluding the trial. Also, the scale assessment should be modified.
Treatment effectiveness of the Fränkel function regulator on Class III malocclusion
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