Asymmetries evaluated with cone-beam computed tomography

With great interest and respect, I read the research reported by Minich et al (Minich CM, Araújo EA, Behrents RG, Buschang PH, Tanaka OM, Kim KB. Evaluation of skeletal and dental asymmetries in Angle Class II subdivision malocclusions with cone-beam computed tomography. Am J Orthod Dentofacial Orthop 2013;144:57-66). First and foremost, I want to express appreciation to the authors for their efforts and contributions in investigating the etiologic factors of Class II subdivision malocclusions. They found significant skeletal and dental differences between the Class I and Class II sides by measuring with cone-beam computed tomography and stated that dental asymmetries account for about two thirds of the total asymmetry. Nevertheless, I have 2 concerns and 2 questions regarding this article.

My first concern is about the subjects, who were divided into 2 groups, an uncrowded group and a crowded group. There was no control group, and the ages of the patients in each group were not clarified. However, it was reported that even people with normal occlusion might have craniofacial asymmetry, and a study has shown that mandibular asymmetry can change with age. Therefore, the differences found between the Class I and Class II sides might have been enlarged or reduced because there was no control group with normal occlusion. In addition, I question the accuracy of the results because the subjects’ ages were not clarified.

My second concern is about 1 landmark. The authors concluded that a significant mandibular asymmetry was identified, so I wondered whether it was contradictory that they chose the genial tubercles to represent the middle of the mandible, which might create confounding factors.

In addition to the concerns above, I have 2 more questions. First, since the tooth-size discrepancy (Bolton index) of the patients was not mentioned, is it necessary to exclude subjects with an obvious tooth-size discrepancy? Second, the authors used the mesiobuccal cusp of the first molar to represent its position. What if the first molars are rotated? Will this affect the result? Or is there a better landmark to represent the molars?

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Asymmetries evaluated with cone-beam computed tomography
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