Three-dimensional morphology of the masseter muscle in patients with mandibular prognathism.

OBJECTIVE To compare the morphology of the masseter muscle in patients with mandibular prognathism with that of normal subjects. METHODS Three-dimensional X-ray computed tomography (CT) was performed on 69 patients with mandibular prognathism and compared with 91 normal subjects. The angle of the muscle direction in relation to the Frankfurt horizontal plane and the area and the ratio of length of the short to long axes (s/l ratio) on the section perpendicular to the muscle direction were measured. RESULTS The mean angle, area and s/l ratio in patients with mandibular prognathism was 76.6 degrees (s.d. 4.4 degrees), 318.3 mm2 (s.d. 77.2 mm2) and 0.312 (s.d. 0.049), respectively. Those of the normal subjects were 65.1 degrees (s.d. 4.4 degrees), 368.3 mm2 (s.d. 97.2 mm2) and 0.393 (s.d. 0.054), respectively. The angle was significantly larger, and the area and s/l ratio were significantly smaller than those of normal subjects (P < 0.001). CONCLUSION The morphology of the masseter muscle in mandibular prognathism is significantly different from that of normal subjects. Our results may be helpful in evaluating the results of orthognathic surgery.

[1]  B. Hillen,et al.  Relationships between Masticatory Muscle Cross-section and Skull Shape , 1984, Journal of dental research.

[2]  A. Hannam,et al.  Relationships between the size and spatial morphology of human masseter and medial pterygoid muscles, the craniofacial skeleton, and jaw biomechanics. , 1989, American journal of physical anthropology.

[3]  A. Hannam,et al.  Relationships Between the Size, Position, and Angulation of Human Jaw Muscles and Unilateral First Molar Bite Force , 1989, Journal of dental research.

[4]  J. H. Koolstra,et al.  An iterative procedure to estimate muscle lines of action in vivo. , 1989, Journal of biomechanics.

[5]  F C van Ginkel,et al.  Comparison of Jaw-muscle Bite-force Cross-sections Obtained by Means of Magnetic Resonance Imaging and High-resolution CT Scanning , 1989, Journal of dental research.

[6]  M. Iwase,et al.  Changes in bite force and occlusal contacts in patients treated for mandibular prognathism by orthognathic surgery. , 1998, Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons.

[7]  B. Prahl-Andersen,et al.  Jaw Muscle Orientation and Moment Arms of Long-face and Normal Adults , 1996, Journal of dental research.

[8]  B. Hillen,et al.  Relationship between the physiological cross-section of the human jaw muscles and their cross-sectional area in computer tomograms. , 1984, Acta anatomica.

[9]  M. Bakke,et al.  Temporalis and masseter muscle activity in patients with anterior open bite and craniomandibular disorders. , 1991, Scandinavian journal of dental research.

[10]  B. Prahl-Andersen,et al.  Relationships between jaw muscle cross-sections and craniofacial morphology in normal adults, studied with magnetic resonance imaging. , 1991, European journal of orthodontics.

[11]  J. H. Koolstra,et al.  Relationships between the orientation and moment arms of the human jaw muscles and normal craniofacial morphology. , 1997, European journal of orthodontics.

[12]  S. Kiliaridis,et al.  Masseter Muscle Thickness Measured by Ultrasonography and its Relation to Facial Morphology , 1991, Journal of dental research.

[13]  H. Kayukawa.  Malocclusion and masticatory muscle activity: a comparison of four types of malocclusion. , 1992, The Journal of clinical pediatric dentistry.

[14]  K. Yoshiura,et al.  Quantitative analysis of masticatory muscles using computed tomography. , 1994, Dento maxillo facial radiology.

[15]  T. van Eijden,et al.  Masseter muscle thickness in growing individuals and its relation to facial morphology. , 1996, Archives of oral biology.

[16]  L. Richards,et al.  Relationship Between Attachment of the Superficial Masseter Muscle and Craniofacial Morphology in Dentate and Edentulous Humans , 1994, Journal of dental research.

[17]  M Bakke,et al.  Ultrasound image of human masseter muscle related to bite force, electromyography, facial morphology, and occlusal factors. , 1992, Scandinavian journal of dental research.

[18]  B. Prahl-Andersen,et al.  A Comparison of Jaw Muscle Cross-sections of Long-face and Normal Adults , 1992, Journal of dental research.

[19]  Weijs Wa.  The functional significance of morphological variation of the human mandible and masticatory muscles. , 1989 .

[20]  A A Lowe,et al.  Relationship Between Jaw Muscle Volume and Craniofacial Form , 1989, Journal of dental research.

[21]  K. Tanne,et al.  Relationship between masticatory muscle activity and vertical craniofacial morphology. , 1998, The Angle orthodontist.

[22]  H. de Bruin,et al.  Muscle activity during mandibular movements in normal and mandibular retrognathic subjects. , 1997, Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons.

[23]  C. Minder,et al.  Correlation between maximum bite force and facial morphology in children. , 1997, The Angle orthodontist.

[24]  G. Throckmorton,et al.  Functional and morphologic alterations secondary to superior repositioning of the maxilla. , 1995, Journal of oral and maxillofacial surgery : official journal of the American Association of Oral and Maxillofacial Surgeons.

[25]  B. Hillen,et al.  Physiological cross-section of the human jaw muscles. , 1985, Acta anatomica.

[26]  Prabhu Nt,et al.  Measurement of masseter and temporalis muscle thickness using ultrasonographic technique , 1994 .

[27]  J. H. Koolstra,et al.  Computer-assisted estimation of lines of action of human masticatory muscles reconstructed in vivo by means of magnetic resonance imaging of parallel sections. , 1990, Archives of oral biology.

[28]  K. Hirose.  [The study of the relationships between the masticatory muscles activity and the craniofacial morphology in mandibular prognathism]. , 1990, Shigaku = Odontology; journal of Nihon Dental College.