Co-ordinated Mandibular and Head-Neck Movements during Rhythmic Jaw Activities in Man

Abstract

Recent observations in man of concomitant mandibular and head movements during single maximal jaw-opening/-closing tasks suggest a close functional relationship between the mandibular and the head-neck motor systems. This study was aimed at further testing of the hypothesis of a functional integration between the human jaw and neck regions. Spatiotemporal characteristics of mandibular and associated head movements were evaluated for 3 different modes of rhythmic jaw activities: self-paced continuous maximal jaw-opening/-closing movements, paced continuous maximal jaw-opening/-closing movements at 50 cycles/minute, and unilateral chewing. Mandibular and head-neck movements were simultaneously recorded in 12 healthy young adults, by means of a wireless opto-electronic system for 3-D movement recordings, with retro-reflective markers attached to the lower (mandible) and upper (head) incisors. The results showed that rhythmic mandibular movements were paralleled by head movements. An initial change in head position (head extension) was seen at the start of the first jaw-movement cycle, and this adjusted head position was retained during the following cycles. In addition to this prevailing head extension, the maximal jaw-opening/-closing cycles were paralleled by head extension-flexion movements, and in general the start of these head movements preceded the start of the mandibular movements. The results support the idea of a functional relationship between the temporomandibular and the cranio-cervical neuromuscular systems. We therefore suggest a new concept for human jaw function, in which "functional jaw movements" are the result of activation of jaw as well as neck muscles, leading to simultaneous movements in the temporomandibular, atlanto-occipital, and cervical spine joints.

Alterações no controle motor mandibular e cervical de crianças com paralisia cerebral

“…The start of head extension generally precedes the beginning of jaw opening, which indicates the anticipatory adjustment of the head position preparatory to jaw movement 5 . The muscles of the jaw and neck have associated movements and changes in one of the structures can disrupt the other.…”

“…Likewise, the correct head extension obtains biomechanical advantages which promote coordination between the head and jaw and enhances force production during bite 5 .…”

“…The functional movements of the jaw are the result of the coordinated activation of the jaw and neck muscles, allowing simultaneous movements between the temporomandibular, atlanto-occipital and cervical spine joints 5 . The results of this study show that motor and functional limitations of children with CP are associated with abnormalities in the control of jaw and head movements during the chewing task.…”

The effect of cervical spine manual therapy on normal mouth opening in asymptomatic subjects

“…10 In addition, in symptomatic patients with whiplash, head extension was absent in opening and closing of the participants' jaw. 17 Our results support these findings of differentiation of symptomatic and asymptomatic populations and suggests that no significant change in jaw opening reflects the absence of alterations often seen in symptomatic populations.…”

“…7 During normal mouth opening, extension occurs at the cervical-cranial junction; and restriction in the upper cervical spine may decrease a patient's mouth-opening capacity. 10 De Laat et al 11 found that segmental limitations in the upper cervical spine (C0-C3) were significantly more present in patients with TMD than controls.…”