We discussed this original article in the May 2018 issue, “Age-dependent biologic response to orthodontic forces” (Alikhani M, Chou MY, Khoo E, Alansari S, Kwal R, Elfersi T, Almansour A, Sangsuwon C, Al Jearah M, Nervina JM, Teixeira CC. Am J Orthod Dentofacial Orthop 2018;153:632-44), in our journal club with great interest and would like to offer a few comments from the discussion.

First, in the “Methods” part of abstract, the authors mentioned a study sample of 18 subjects with Class II Division 1 malocclusion requiring 4 first premolar extractions, but in the detailed “Material and methods” section, they mentioned “Class II Division 1 malocclusion that required extraction of both maxillary first premolars.” In Table IV (Morphologic characteristics of the patients), U1-SN values of 107.9° ± 4.1° and IMPA values of 97.7° ± 3.2° along with the cephalometric parameters in Table I as inclusion criteria show that no patients with severe skeletal Class II malocclusion were included. This information is contradictory. Were the patients treated with only 2 maxillary first premolar extractions and finished in a Class II molar relationship? Or was a standard camouflage extraction protocol for Class II malocclusion in the form of extractions of maxillary first premolars and mandibular second premolars used to finish the patients in an Angle Class I relationship, and did the patients have any other orthodontic treatment procedure? Since the authors mentioned in the abstract that patients with Class II Division 1 malocclusion requiring 4 first premolar extractions were included, then why was it required in all patients? The dentoalveolar characteristics and cephalometric parameters given do not corroborate the planned extraction procedure for all patients.

Second, in the legend to Figure 1, it is mentioned that retraction started after first molar extractions; this may be a printing error, but it was not expected because readers usually read the abstract and figure descriptions briefly and received a confusing picture about the methodology.

Although the topic of research is relevant in this well-designed study and appreciable efforts were made to remove confounding factors, kindly acknowledge and clarify the above-mentioned points for readers’ benefit.