Relationship Between the Masticatory Muscles and Mandibular Skeleton in Mandibular Prognathism With and Without Asymmetry

Kwon, Tae-Geon; Lee, Ki-Ho; Park, Hyo-Sang; Ryoo, Hyun-Mo; Kim, Hyun-Jung; Lee, Sang-Han

doi:10.1016/j.joms.2006.09.024

« Previous Next »Journal of Oral and Maxillofacial Surgery
Volume 65, Issue 8 , Pages 1538-1543, August 2007

Relationship Between the Masticatory Muscles and Mandibular Skeleton in Mandibular Prognathism With and Without Asymmetry

Tae-Geon Kwon, DDS, PhD
- Associate Professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, Korea.
- Address correspondence and reprint requests to Dr Kwon: Department of Oral and Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Samduck 2 Ga, Jung Gu, Daegu, 700-421, Korea
Ki-Ho Lee, DDS, MS
- PhD Student, Department of Oral and Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, Korea.
Hyo-Sang Park, DDS, PhD
- Professor, Department of Orthodontics, School of Dentistry, Kyungpook National University, Daegu, Korea.
Hyun-Mo Ryoo, DDS, PhD
- Professor, Department of Cell and Developmental Biology, School of Dentistry, Seoul National University, Seoul, Korea.
Hyun-Jung Kim, DDS, PhD
- Professor, Department of Pedodontics, School of Dentistry, Kyungpook National University, Daegu, Korea.
Sang-Han Lee, DDS, PhD
- Professor, Department of Oral and Maxillofacial Surgery, School of Dentistry, Kyungpook National University, Daegu, Korea.

Purpose

The purpose of the present study was to evaluate the relationship between masticatory muscle volume and mandibular skeletal measurements in patients with and without facial asymmetry. This was done in order to determine whether asymmetric mandibular prognathism is related to masticatory muscle asymmetry.

Patients and Methods

The study was conducted with 40 adult patients with mandibular prognathism composed of 2 groups, the asymmetry group (n = 20) and the nonasymmetry group (n = 20). Using 3-dimensional reformatted computed tomography (CT) images, the volume of masticatory muscle (masseter, temporal, medial, and lateral pterygoid muscles) and various skeletal measurements (hemimandibular volume, ramal height, body length, mandibular length, gonial angle) were evaluated and compared. The right-left difference was expressed by an asymmetry index {(right − left)/left, %}.

Results

The results showed that in the asymmetry group, the longer mandibular side (contralateral side of chin deviation) exhibited longer ramal and body length, a wider gonial angle, and more hemimandibular volume with less medial pterygoid volume, whereas the nonasymmetry group did not show a statistical bilateral difference between the skeletal and muscular measurements. The correlation analysis showed that patients with facial asymmetry did not have similar patterns of muscle-bone relation as compared with the symmetrical subjects.

Conclusion

In patients with mandibular prognathism, the bilateral difference in muscle volume would reflect the difference in the spatial anatomy of a skeletal structure and could not predict mandibular skeletal asymmetry.