Relation between facial morphology and activity of the masticatory muscles

Abstract

Summary The relation between muscle activity and facial morphology was studied in twenty‐five boys and twenty‐seven girls, aged 9–11 years. The activity in the anterior and posterior parts of the temporal muscle, the masseter muscle and the upper lip was recorded bilaterally with the mandible in postural position and during chewing, swallowing and maximal bite. The electromyograms were analysed in respect of maximal mean voltage amplitude and the duration of muscle activity. Facial morphology was studied with the aid of profile roentgenograms and model analysis. The activity in postural position was found to be greater in the posterior than in the anterior part of the temporal muscle. The average mean voltage amplitude in the temporal and masseter muscles was greatest during maximal bite, smaller during chewing and smallest during swallowing. In the orbicularis oris muscle the activity was greater during the opening phase of the chewing cycle than during the closing phase. In postural position the activity in the anterior and posterior parts of the temporal muscle were positively correlated. The amplitudes in the anterior and posterior parts of the temporal muscle and in the masseter muscle were positively correlated during chewing, swallowing and maximal bite. The amplitudes in these muscles during chewing were positively correlated with those in the same muscles during maximal bite. During swallowing the amplitude in the upper lip was negatively correlated with that in the anterior part of the temporal muscle. The clearest correlations between muscle activity and facial morphology were found during chewing and maximal bite. During these functions the amplitudes in the temporal and masseter muscles were large in cases with a tendency to parallelism between the jaws bases and between the mandibular occlusal line and the mandibular line. These cases with considerable muscle activity are characterized by rectangular shape of the face in profile and small lower face height.

Association between mandibular posterior alveolar morphology and growth pattern in a Chinese population with normal occlusion

“…Finally, the molars reach a balanced position (Masumoto et al, 2001). The lower molars are close to the attachment area of the masseter (Ingervall and Thilander, 1974;Tabe, 1976), and therefore are more influenced by the force of the masseter. Subjects with horizontal growth pattern have a stronger masseter (Ingervall and Helkimo, 1978), and it is not surprised that the molars of patients with the horizontal growth pattern have a greater buccal inclination compared to the molars of those with the vertical growth pattern.…”

“…The morphology of the tooth-alveolar bone complex is an important factor in orthodontic treatment planning, assessment of treatment progress, and the determination of treatment outcomes (Aasen and Espeland, 2005). The structure of the tooth-alveolar bone complex changes following alterations in loading by forces developed through the dentition and joint as the muscles contract during function (Ingervall and Thilander, 1974;Dechow and Hylander, 2000). Various growth patterns have different biting forces and biological adaptations, and therefore, result in different mandibular toothalveolar structures (Dechow and Hylander, 2000).…”

Electromyographic Activity of Masseter and Temporal Muscles with Different Facial Types

“…17 EMG evaluations of masticatory muscles have produced divergent results when individuals with different vertical facial growth are compared. Some authors have observed that the amplitude of EMG values in temporal 1,2,6 and masseter 1,3,6 muscles is always greater in short-faced individuals. Some articles reported that the longer the face of an individual, the greater the EMG activity of the temporal muscle.…”

“…Their function and anatomy have been evaluated by electromyographic (EMG) exams, [1][2][3][4][5][6][7][8][9] bite force, 10 computed tomography of muscle thickness, 11 ultrasonography 5,[12][13][14][15] and magnetic resonance, 16 in addition to immunohistochemistry evaluations of muscular fibers. 17 EMG evaluations of masticatory muscles have produced divergent results when individuals with different vertical facial growth are compared.…”

A cephalometric comparison of skulls from the fourteenth, sixteenth and twentieth centuries

“…It is clear however that bread was the staple food of many and that the grain from which it was made varied from place to place. 13 A possible relationship between facial growth and muscle size or activity has been suggested by several studies using human subjects [14][15][16][17][18][19][20] and the hypothesis that jaw size may be affected adversely by reduced mastication has been supported by the results of animal experiments. 21,22 Others have cast doubt on the muscle-exercise theory, considering that normal jaw growth would proceed over a wide range of activity and that only an altogether exceptional degree of lack of use might affect it.…”