Authors’ response

We want to thank Jingyu Li et al for the feedback on our study evaluating asymmetries in Class II subdivision malocclusions using cone-beam computed tomography (CBCT).

Dr Li brought up a few concerns regarding our subjects. The first concern was that we divided our study sample into 2 groups, a crowded group and an uncrowded group, but we did not have a control group of normal Class I patients. We were focusing on Class II subdivision malocclusions and wanted to know the difference between the Class I and the Class II sides. We were not initially interested in comparing these groups with a Class I control group. However, after completing our research, we think it would be a great continuation of the study to test this method and technique on a normal Class I control sample to investigate with CBCT whether similar asymmetries can be found in Class I occlusion groups.

A second question from Dr Li was that we did not define a specific age group. We decided to use the permanent dentition as a criterion instead of a specific age (patients had to have all permanent teeth present from first molar to first molar). Dental age and chronologic age can vary quite a bit, so we decided to use dentition as the selection criterion. Also, Class II subdivision malocclusions are difficult to find; if we had limited our sample to a specific age group—eg, age 18 and older to represent nongrowing patients—we would have had a difficult time finding enough patients to study. In addition, orthodontists usually begin treating patients based on when the permanent teeth have erupted, so this selection criterion better represents real clinical situations.

Another question was in regard to the landmark we chose to represent the middle of the mandible. Dr Li felt that our results might be contradictory because we chose the midpoint between the genial tubercles. We are not sure why this question was posed. The significant difference we found for the mandible was for the measurement between the mandibular and mental foramina. This measurement does not include the genial tubercles or the mandibular midline. We are open to using another landmark for the mandibular midline, but what other landmark can be easily identified on CBCT images to represent the midline of the mandible? The mandible is 1 piece, and it is much different to select a point on a 3-dimensional image than on a 2-dimensional x-ray.

Dr Li asked whether we considered the Bolton Index in our sample. Yes, we excluded patients with an obvious tooth-size discrepancy. Lastly, he asked whether there is a better landmark to represent the permanent first molars instead of the mesiobuccal cusp tip because the molar could be rotated and possibly affect the results. This is a good point. Yes, this could affect the results, but we still chose this point because it is easily identifiable, reliable, and integral to Angle’s categorical definitions. You could attempt to find a point in the middle of the pulp chamber or the furcation, but we thought that it would be more difficult to reliably find this location.

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Apr 6, 2017 | Posted by in Orthodontics | Comments Off on Authors’ response
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