Three-dimensional computed tomographic assessment of mandibular muscles in growing subjects with different vertical facial patterns

Alwyn Wong,Michael G. Woods,Damien Stella

doi:10.21307/aoj-2020-107

Abstract

Abstract Aim The present study was undertaken to assess the relationship between the mandibular muscles and dentofacial skeletal morphology in children with different underlying vertical facial patterns, using three-dimensional computed tomography (3D-CT). Method Thirty children (mean age 12.24 ± 1.57 years) underwent cranial CT examination for diagnostic purposes. 3D-CT images were reconstructed for the evaluation of the cross-sectional size, volume, and spatial orientation of the masseter and medial pterygoid muscles. These muscle parameters were also assessed in relation to the vertical facial pattern, gender and skeleto-dental form. Results Significant differences were found in muscular angulation for subjects with different underlying patterns. Greater masseter volumes were associated with increased facial width. Greater intermolar widths were found in brachyfacial subjects, with less acute muscular angulations in relation to horizontal reference lines, compared with dolichofacial subjects. This was also more obvious in the maxillary arch. Conclusion Clinicians should note the likely differences in masseter and medial pterygoid orientation and volume in subjects with different underlying vertical facial patterns and that these differences may, in turn, be related to both facial skeletal width and naturally-occurring transverse dental arch dimensions.

Highlights

For some time, there has been a general acceptance that growth and development of craniofacial forms are dependent, at least in part, on the functional state of the surrounding soft tissues as well as the patient’s underlying genetic make-up.[1,2,3] It is, not known whether genetically determined facial morphology determines the size and strength of the mandibular muscles or whether, instead, a particular muscular form influences the form of the dentofacial complex.[2]
Brachyfacial subjects, with less acute muscular angulations in relation to horizontal reference lines, are likely to have greater intermolar widths than dolichofacial subjects. This applies more to the maxillary arch than to the mandibular arch

Summary

Introduction

There has been a general acceptance that growth and development of craniofacial forms are dependent, at least in part, on the functional state of the surrounding soft tissues as well as the patient’s underlying genetic make-up.[1,2,3] It is, not known whether genetically determined facial morphology determines the size and strength of the mandibular muscles or whether, instead, a particular muscular form influences the form of the dentofacial complex.[2]. It has been reported that stronger and larger mandibular elevator muscles are generally accompanied by wider transverse facial dimensions.[1,4,5,6,7] these individuals often display a short anterior face height, long posterior face height, a larger posterior to anterior face height ratio, parallelism of the jaw bases, a small gonial angle and larger maxillary transverse dental arch dimensions.[8,9,10,11]

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