Comment on “Computed Tomography Evaluation of Craniomandibular Articulation in Class II Division 1 Malocclusion and Class I Normal Occlusion Subjects in North Indian Population”

Clear statement of objective, appropriate location of landmarks and removal of subjective bias in measurement is essential in all kinds of research, especially, orthodontics. The research design should be rationalistic, purposeful, and in accordance with the objectives of the study. In this communication, we highlight the errors in research design, measurement, analysis, and inferences drawn with the help of a published article as the primary source to explain these simple but useful points. 1. Unclear Objective The authors state the purpose of study is “to investigate the Craniomandibular articulation morphology and position of condyle in mandibular fossae in Angle’s class I normal occlusion and Angle’s class II division 1 malocclusion”; however, no objective attempt has been made to establish distinction between two classes, and in the absence of any such distinction between two classes, it is difficult to assume that the articulation morphology claimed to be of a particular class is a true representation of that particular class and not the other class. It is disappointing to see that, despite using quantitative tools, the authors have tried to make only “within-class comparisons” and no attempt has been made to compare the morphological parameters “between two classes” to differentiate and establish any finding to be representative of a particular class. We fail to understand if the purpose of the study was not to differentiate between two occlusal classes, then why the entire study has been carried out taking two occlusal classes separately. In our view, if the purpose of study was to compare between left and right sides, then there was no need to differentiate between two classes. Moreover, if this was the purpose, then a combined assessment of two classes would have given a better ground for differentiation owing to enhanced sample size. 2. Statistical Tools There is a lot of confusion and a number of errors while stating and using the statistical tools. The authors have measured different morphological parameters using a continuous scale. The basis of their measurements happens to be based on subjective interpretation/tracings. The authors have mentioned using two examiners to rule out subjective error in measurement. However, they have mentioned to have used K-score for assessment of interexaminer reliability; it seems that authors are referring here to kappa-statistic. To the best of our knowledge, Kappa-statistic is used to compare the ordinal data or ordinal transformation of continuous data [1]. For continuous data, paired “ ”-test, Pearson