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relationships in mixed dentition patients treated with rapid maxillary expansion. A prospective clinical study. Angle Orthod 2010;80:230-8. 8. Zimmerman DW. A note on preliminary tests of equality of variances. Br J Math Stat Psychol 2004;57:173-81. Rapid palatal expansion, with and without alternating constriction W e read the article "Effect of maxillary protraction with alternating rapid palatal expansion and constriction vs expansion alone in maxillary retrusive patients: a single-center, randomized controlled trial" in the October 2015 issue with great interest. 1 The study compared the effects of facemask protraction combined with alternating rapid palatal expansion and constriction (Alt-RPE/C) vs rapid palatal expansion alone in maxillary retrusive patients and concluded that Alt-RPE/C with maxillary protraction positively affects the forward movement of the maxilla compared with rapid palatal expansion alone. The confounding factors such as age and sex were not mentioned in the article.Whereas we do accept that this study was a welldesigned randomized control trial providing considerable evidence for clinicians to adopt the new expansion regimen, we request the authors to consider the following.1. In this study, the achievement of a positive overjet was the treatment completion criterion. The authors concluded that Alt-RPE/C with maxillary protraction might result in a greater orthopedic-orthodontic Table II. Initial age, distribution of the Michigan and Bauru subjects among the evaluated groups, sex distribution between the Michigan and Bauru subjects and among evaluated groups Variable Michigan Bauru P Initial age, Michigan 3 Bauru subjects (y), Mean (SD) 8.68 (60.75) 8.71 (60.97) 0.873* Group 1A, Michigan 3 Bauru subjects (%) 60 40 0.869 y Group 2A, Michigan 3 Bauru subjects (%) 70.8 29.2 Group 2B, Michigan 3 Bauru subjects (%) 65.6 34.4 Group 3A, Michigan 3 Bauru subjects (%) 66.2 33.8 Male Female P Michigan subjects, male 3 female (%) 58.4 41.6 0.091 y Bauru subjects, male 3 female (%) 44.4 55.6 Group 1A, male 3 female (%) 63.3 36.7 0.106 y Group 2A, male 3 female (%) 45.8 54.2 Group 2B, male 3 female (%) 68.7 31.3 Group 3A, male 3 female (%) 46.3 53.7 *t tests.; y chi-square.