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Korean J Orthod 2020; 50(6): 361-362

Published online November 25, 2020 https://doi.org/10.4041/kjod.2020.50.6.361

Copyright © The Korean Association of Orthodontists.

READER’S FORUM

Hyun-Joo Jeong

Department of Orthodontics, College of Dentistry, Kyung Hee University, Seoul, Korea

This is an Open Access article distributed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.

Jun-Young Kim, Hee-Keun Park, Seung-Woo Shin, Jin Hoo Park, Hwi-Dong Jung, Young-Soo Jung

Three-dimensional evaluation of the correlation between lip canting and craniofacial planes.

- Korean J Orthod 2020;50:258-267

Q1. Patients with skeletal Class III malocclusion were selected for the study. Do you think the anteroposterior skeletal relationship in skeletal Class III patients affects the conclusion that lip canting is strongly correlated with the mandibular symmetry plane than maxillary canting?

Q2. Although the amount of menton deviation is similar, the asymmetry pattern may be different since it could be yaw-, roll- and translation-dominant. Do you think the mandibular asymmetry type influences on lip canting differently when the menton deviation is similar?

Q3. It was mentioned that there is a difference between skeletal asymmetry and soft tissue asymmetry. In this study, the mandibular symmetry plane showed a strong relationship with lip canting at rest. In a posed smile, do you think the correlation will change? For example, do you expect the maxillary canting shows a strong relationship due to muscle originating?

Questioned by

Hyun-Joo Jeong

Department of Orthodontics, College of Dentistry, Kyung Hee University, Seoul, Korea

We would like to express our appreciation for the interest in our published article.

A1. Patients with skeletal III relationships show prominent mandibular prognathism and it may be accompanied by facial asymmetry, especially if one side shows condylar hyperplasia. In this study, mandibular symmetry plane inclination and maxillary canting showed the similar tendency due to compensatory maxillary growth according to mandibular growth. Our research showed that mandibular symmetry plane is more strongly correlated with the lip canting and skeletal III relationship may affect the conclusion.

A2. We appreciate your insightful feedback. We are planning further research about the relationship between lip canting and mandibular shape including yaw-, roll-, and translation-dominance. We expect these factors also affect lip canting in patients with similar amount of menton deviation. Further research will be followed.

A3. As mentioned, lip canting is affected by a number of factors, including the nature of soft tissue and muscle activity, especially when smiling. It is known that activation of the zygomaticus major muscle has a major effect on lip tilting and asymmetry when making a smile.1 Furthermore, Cho et al.2 reported that muscle activity may be affected by psychological factors when laughing. Therefore, in order to evaluate the effect of the lip canting during a smile, electromyography as well as evaluation of the size and position of the facial muscles may be necessary.1

Considering your question, we believe that the maxillary canting may have more effect on the lip canting while smiling, especially due to the attachment of the zygomaticus major muscle, but further research will be needed on this.

Replied by

Jun-Young Kim and Young-Soo Jung

Department of Oral and Maxillofacial Surgery, Yonsei University College of Dentistry, Seoul, Korea

References

  1. Epstein LH. Perception of activity in the Zygomaticus major and Corrugator supercilii muscle regions. Psychophysiology 1990;27:68-72.
    Pubmed CrossRef
  2. Cho JH, Kim EJ, Kim BC, Cho KH, Lee KH, Hwang HS. Correlations of frontal lip-line canting with craniofacial morphology and muscular activity. Am J Orthod Dentofacial Orthop 2007;132:278.e7-14.
    Pubmed CrossRef