A three-dimensional analysis of masticatory muscles in laterognathism

ABSTRUCT

Purpose

By using three-dimensional (3-D) CT imaging, the maxillofacial bones and muscles can be observed from any desired angles and analyzed the bone and muscles simultaneously. However, no studies have investigated the three dimensional analysis of muscles in jaw deformity. The purpose of this study was to examine the relationship between the morphology of the masticatory muscles and the craniofacial skeleton in the patients with facial asynmetry.

Methods

Eight Japanese normal female adults and 10 female adult patients with laterognqthism were participated in this study. The 3-D CT images of their craniofacial skeleton and masseter, medial pterygoid and lateral pterygoid muscles were recon-structed. Then, 6 skeletal and 7 muscle variables were measured for each subject.

Results

Significant positive correlations were found among the volume of the masti-catory muscles in the normal adults, but not found in patients with mandibular laterognathism. The muscular variables showed significant positive correlations with skeletal variables in normal subjects, but few significant correlations were found in the patients with laterognathism.

Conclusions

This study suggestted that the balance between masticatory muscles and the balance between muscles and skeleton collapsed in the patients with mandibu-lar laterognathism.

Keywords:

• Computed tomography
• Three-dimensional
• Masticatory muscles
• Laterognathism

Acknowledgments

We are grateful to the staff of the Radiology and Orthodontic Departments of the Attached Hospital of Kyushu University for their assistance in taking computed tomograms, and to Dr. Gaylord S. Throckmorton for reading the manuscript. A part of this study was supported by the Grant-in-Aid for Scientific Research (B) 19390531, Encouragement of Young Scientists (B) 18791561 and Exploratory Research 19659542 from the Japan Society for the Promotion of Science.