Anatomical Characteristics of the Masseter Muscle in Mandibular Prognathism

Abstract

Mandibular prognathism causes functional and esthetic problems. Therefore, many studies have been conducted to understand its etiology. Following our previous study, which revealed that the major characteristic of the mandible with prognathism is the volume/length ratio of the mandibular body and condyle, we analyzed the volume and orientation of the masseter muscle, which inserts into the mandibular body, expecting that the difference in the size of the masseter muscle causes the difference in the mandibular size. This study compared the masseter muscle of the participants in the prognathic group to those in the normal group on the volume/length ratio and orientation. The masseter muscle ratios (volume/length); the angle between the superficial and deep head of the masseter muscle; and the three planes (the palatal, occlusal, and mandibular) were analyzed. A total of 30 participants constituted the normal group (male: 15, female: 15) and 30 patients, the prognathic group (male: 15, female: 15). The results showed that the volume/length ratio of the masseter of the normal group was greater than that of the prognathic group (p < 0.05). In addition, the orientation of both the superficial and deep head of the masseter of the participants in the normal group was more vertical with respect to the mandibular plane than that of the prognathic group (p < 0.05). We concluded that the mechanical disadvantage of the masseter muscle of the prognathic group is attributed to mandibular prognathism.

Volumetric Change in the Masseter and Lateral Pterygoid after Mandibular Setback

“…However, this study also investigated the changes in the lateral pterygoid muscle. As revealed in our previous studies [ 1 , 2 , 3 ], in mandibular prognathism, both the masseter muscle and the lateral pterygoid muscle showed significant differences from that of the normal mandible. To the best of our knowledge, no previous studies have examined the changes in the lateral pterygoid muscle after a mandibular setback.…”

“…Mandibular prognathism is a morphological abnormality occurring in the oral and maxillofacial regions, resulting in aesthetic and functional problems [ 1 , 2 , 3 , 4 ]. Although corrective and surgical methods are available for the treatment of mandibular prognathism, surgery is the most appropriate treatment for most adults [ 5 , 6 , 7 ].…”

“…However, young patients can be treated with orthodontic methods, which include timing treatment options, growth prediction of the mandible, and control of the growth patterns. Therefore, many studies have been conducted on elucidating the growth pattern of the mandible and the factors affecting it [ 1 , 2 , 3 , 8 ].…”

“…In our previous studies [ 2 , 3 ], we compared the masseter and lateral pterygoid muscles of class I and class III patients. The results of the studies showed that the volume-to-length ratios of the masseter and lateral pterygoid muscles in the class I group were larger than those in the class III group.…”

Three-Dimensional Postoperative Results Prediction for Orthognathic Surgery through Deep Learning-Based Alignment Network

“…Dentofacial dysmorphosis is characterized by retrognathism, prognathism, and asymmetry [ 1 , 2 , 3 ]. Various orthognathic surgery techniques have been applied for treatment [ 4 , 5 ].…”