We thank Drs Thiesen and Kim for their interest on our article, “Evaluation of facial hard and soft tissue asymmetry using cone-beam computed tomography,” in the February issue of the American Journal of Orthodontics and Dentofacial Orthopedics .
In our study, we stated that patients with less than 4 mm of soft-tissue menton deviation from the midsagittal reference line by clinical evaluation were categorized as symmetric, and those with 4 mm or more deviation were categorized as asymmetric. Haraguchi et al mentioned that faces having skeletal deviations of more than 4 mm are more likely to be judged with soft tissue asymmetry. We know that some authors accept 2 mm of bone and soft tissue deviation as asymmetric. However, other studies recognized 4 mm of menton deviation as the limit to distinguish the asymmetry and the control groups.
It was reported that thin soft tissue layers such as in the menton region are related to the underlying skeletal units in a 1:1 ratio. Consequently, a 4-mm skeletal deviation may demonstrate approximately the same extent of soft tissue asymmetry. As mentioned in the article, the findings also agree that positive correlations were present between angular as well as linear measurements from the hard and soft tissue menton. Indeed, individual characteristics such as the weight of the patient may influence the results. Lee et al mentioned that soft tissue chin deviation angular measurements for the control, mild, and severe asymmetry group were 1.1°, 2°, and 3.64°, respectively. In our study, the angular measurements of the chin deviation were identical for the control group (1.1°); this supported the control group selection. On the other hand, the chin deviation of the asymmetry group was 2.79°, categorizing this group as a moderate asymmetric group, and not a severe one.
Overall, we have mentioned that the control group also showed mild asymmetries. In further studies, facial asymmetry evaluated with more subgroups (such as soft tissue menton deviations of 0-1 mm, 1-2 mm, 2-3 mm, 3-4 mm and so on) to distinguish the exact limits of control and asymmetry may be advisable.
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