Electromyographic Heterogeneity in the Human Temporalis and Masseter Muscles during Dynamic Tasks Guided by Visual Feedback

Abstract

The complex architecture of the human jaw muscles suggests regional differences in function within these muscles. This study examines the way the temporalis and masseter muscle regions are activated when free mandibular movements with various speeds and against various external leads are carried out guided by visual feedback. Electromyographic (EMG) activity was registered in six temporalis and three masseter muscle regions with bipolar fine-wire electrodes. Recordings were made during open/close excursions, protrusion/retrusion movements, and laterodeviations. During open/close excursions and protrusion/retrusion movements, an anterior and posterior temporalis part could be distinguished, whereas during laterodeviations a more complex partitioning of this muscle was observed. During the protrusion/retrusion movements and the laterodeviations, the temporalis muscle demonstrated higher EMG peak activities than the masseter muscle, and within the masseter muscle the deep masseter showed higher EMG peaks than the superficial one. In contrast to this, during the open/close excursions the masseter showed higher peak activities than the temporalis muscle, while the superficial masseter showed higher EMG peak activities than the deep masseter. Within the deep masseter, differences were also found. During open/close excursions, the anterior deep region demonstrated higher EMG peak activities than the posterior region, whereas during protrusion/retrusion and laterodeviations the posterior deep region showed higher peaks. In general, speed had a greater effect on the EMG peak activity than external load. Only during laterodeviations did speed and load equally influence peak activity in both the deep and superficial masseter. During protrusion/retrusion movements, load showed no significant effect on EMG peak activity in the masseter muscle. A general finding was that, according to task, different regions were activated preferentially. This points to a partitioning of the excitatory command of the motoneuron pool.

Growth hormone receptor gene variant and three-dimensional mandibular morphology

“…20 The temporal muscle is attached to the coronoid process, and negative correlations have been observed between temporal muscle activity and mandibular plane and gonial angle and overjet. 21,22 A previous study examining the relationship between maxillofacial morphology and coronoid process morphology 23 revealed that the morphology of the coronoid process influences not only mandibular position but also maxillary position and dentition. A previous report describing the measurement of the coronoid processes using CBCT imaging 24 revealed that, in comparison with skeletal pattern differences, differences related to gender were greater in terms of craniofacial morphology and the volume and height of the coronoid processes.…”

Modulation of mandibular loading and bite force in mammals during mastication

“…Some workers have related variation in EMG patterns to variation in bite force orientation and magnitude during isometric biting on a bite force transducer (Blanksma et al, 1997); others have measured bite force orientations and/or magnitudes from intra-oral implants in edentulous (MericskeStern et al, 1992) or partially dentate (Lundgren and Laurell, 1986) subjects. These studies have various limitations, the most serious of which is destruction of the periodontal ligament afferents employed to modulate bite force production (Trulsson, 2006).…”

Burst characteristics of daily jaw muscle activity in juvenile rabbits

“…Jaw muscles participate in a wide range of oral behaviors, during which timing and coordination between the muscles differ (Langenbach et al, 1992;Blanksma et al, 1995Blanksma et al, , 1997. These variations in muscle use can be related to differences in duty time between the muscles (Langenbach et al, 2004;van Wessel et al, 2005).…”