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Variations in the facial muscles at the angle of the mouth
Author(s) -
Shimada Kazuyuki,
Gasser Raymond F.
Publication year - 1989
Publication title -
clinical anatomy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 71
eISSN - 1098-2353
pISSN - 0897-3806
DOI - 10.1002/ca.980020302
Subject(s) - anatomy , medicine , cadaver , sagittal plane , orthodontics
The Latin term modiolus literally means “the nave of a wheel” and in dentistry refers to the point lateral to the angle of the mouth where several facial muscles converge. It has been described as coinciding with a muscular or tendinous node in the cheek and is considered to be important clinically. The facial muscles that insert in the vicinity of the mouth angle are the levator anguli oris, zygomaticus major, risorius, buccinator, and depressor anguli oris. The arrangement of these muscles in relation to the angle of the mouth was studied in 147 cadavers (279 sides) of the Mongoloid (Japanese) and Caucasian races. Considerable variation in the pattern of convergence was found. The variations were classified into three types as follows. Type A : location of the muscle convergence was lateral to the angle of the mouth. Type B : convergent area was located above the angle. Type C : convergent area was located below the angle. When the two races were considered together type C occurred most frequently (42.3%) followed closely by type B (41.2%). The arrangement described in textbooks ( type A ) occurred least frequently (16.5%). The frequency of appearance of convergent types according to race also is given. The gross observations do not support the existence of a nodular modiolus. In addition, the muscles that are supposed to contribute to the nodule usually do not converge lateral to the mouth angle but rather converge either above or below the angle.