Letters to the editorVariable torque in self-ligating brackets W e read and discussed with great interest the article by Calil et al (Calil RC, Marin Ramirez CM, Otazu A, Torres DM, Gurgel JA, Oliveira RC, et al. Maxillary dental and skeletal effects after treatment with self-ligating appliance and miniscrewassisted rapid maxillary expansion. Am J Orthod Dentofacial Orthop 2021;159:e93-e101). We want to congratulate the authors on their interesting study and also raise a few questions.The study mentioned that group 2 treated with miniscrew-assisted rapid palatal expander consisted of 16 patients obtained from the archives of Advanced Dentistry Institute, Asuncion, Paraguay, with no additional treatment. However, in the Discussion, the authors stated that the group 1 sample was retrospective, whereas the group 2 patients were being treated prospectively and were on a corrective orthodontic phase. This is a contradiction; kindly clarify. Furthermore, it was mentioned that patients in whom midpalatal suture opening did not occur were excluded. So, how many patients were excluded? What was the final sample size? Did the final sample size affect the power of the study? In addition, explain the variation of group 2 sample size in Tables III and IV (n 5 18) compared with Tables I and II (n 5 16).The study concluded a significant decrease in buccal bone thickness in the canines and premolars but a significant increase in buccal inclination of only premolars in the self-ligating group when compared with the miniscrew-assisted rapid palatal expander group. The self-ligating sample was obtained from the archives of 3 different institutes of
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