Relation between masseter muscle volumes and mandibular body lengths in skeletal Class III adult female cases without severe mandibular asymmetry. Issue 3 (3rd July 2022)

• Record Type: Journal Article
• Authors: Fujimoto, Kouta; Sasaki, Au; Kawajiri, Akemi; Yamaguchi, Koji; Oshima, Takafumi; Togane, Yuri; Otsuka, Yuichiro; Suda, Naoto
• Is Part Of: Clinical and Investigative Orthodontics. Volume 81:Issue 3(2022)
• Page Start: 144
• Page End: 152
• Publication Date: 2022-07-03
• Subjects: Cranial vault -- mandibular fossa -- mandibular body length -- masseter volume
• DOI: 10.1080/27705781.2022.2094110
• Languages: English
• ISSNs: 2770-5781

Abstract

ABSTRACT: Objective: As reported in our pilot study using skeletal Class III adult female cases without severe mandibular asymmetry (Kawajiri A, et al, Jpn J Jaw Deform. 2019;29:31-41), cranial vaults with unilateral posterior deformation had posteriorly positioned mandibular fossae on the same side, and the longer mandibular bodies were seen with more posteriorly-positioned mandibular fossae. These findings suggest that mandibular body length compensated the A-P position of the mandibular fossa to prevent facial asymmetry. However, the used subjects in our pilot study were selected by two-dimensional P-A cephalograms. Thus, as the first purpose, three-dimensional case selection was performed, and craniofacial structure was examined in subjects. As the second purpose, the relation between the mandibular body lengths and the masticatory muscle volume was examined. Materials and Methods: CT images of 32 adult female patients with skeletal mandibular protrusion were used in this study. The lateral deviation of Pog was less than 3 mm in all cases. The 3D analysis was performed on CT images. The cranial vault shape, the position of the mandibular fossae and the length of the mandibular bodies were analyzed. The masseter and medial pterygoid muscles were reconstructed and analyzed. Results: The present findings reproduced the results in our previous pilot study. The volume of the masseter muscles, but not the medial pterygoid muscles, had a significant positive correlation with the mandibular body lengths. Conclusion: A novel mechanism for preventing mandibular asymmetry was proposed. Both hard and soft craniofacial tissues are likely to be involved in this mechanism.