We read with great interest the article entitled “Evaluation of facial hard and soft tissue asymmetry using cone-beam computed tomography” in the February issue of the Journal . The authors evaluated facial asymmetry 3 dimensionally using cone-beam computed tomography and compared the right and left facial hard and soft tissues linearly and volumetrically. They used an innovative and interesting methodology, so we need to congratulate them.
However, their outcome was established using a wrong assumption. They stated that “Patients with less than 4 mm of Me′ deviation from the midsagittal reference line were categorized as symmetric and comprised the control group, whereas patients with 4 mm or more of Me′ deviation comprised the asymmetry group, similar to the study of Haraguchi et al.” However, what Haraguchi et al really stated in their article was “The results…suggest that faces having skeletal chin deviation of more than 4 mm are likely to be judged also with soft tissue facial asymmetry.”
Therefore, it seems that skeletal deviation must be equal to or greater than 4 mm to render the asymmetry visible in a person’s face. Whenever the degree of asymmetry is lower, the condition tends to be considered mild and unperceivable. Nevertheless, asymmetry perception or blinding will also depend on individual characteristics, such as soft tissue thickness in that region. For this reason, other authors consider an asymmetrical face as having bony deviations equal to or greater than 2 mm. That is why even nowadays we still have some doubts for establishing the criteria for facial asymmetries. It is particularly important since, without specific limits, studies usually use different boundaries.
Its seems therefore that Nur et al evaluated severe asymmetric cases. But the mentioned point raises real importance, since their control group had a soft tissue menton deviation of 2.17 ± 1.11 mm. Several authors have stated that a soft tissue chin deviation of more than 2 mm is considered asymmetry.