Mandibular deviations in TMD and non-TMD groupsposture

The Journal of Clinical Pediatric Dentistry Volume 25, Number 2/2000 147 INTRODUCTION The craniomandibular system is designed to function as a unit and its parts cannot be considered independently. The idea of a malfunctioning unit is reflected in the term, craniomandibular disorders, (CMD) which is a collective term embracing a number of clinical problems that involves the masticatory musculature, the temporomandibular joint (TMJ) or both. The guidelines of the American Academy of Craniomandibular Disorders propose that abnormal jaw and head position are suspected as perpetuating factors affecting CMD. Mohl supports this notion and adds that head posture appears to have the most significant and immediate effect on mandibular postural rest position. Dysfunction of one component of this complex system frequently affects other components of the craniomandibular system as well as adjacent systems. Rocobado found this to be true and has stated that when mandibular position is altered in space in all planes, it is a result of occlusion, muscle activity, and head and neck posture. The function and resting position of the head has been shown to be directly dependent on the posture of the cervical spine. Head posture, however, always dominates. When dealing with the upper quarter of the body, cervical spine dysfunction will lead to a compensatory change in head position. The center of gravity of the head is located slightly anterior to the cervical spine. Unless the posterior muscular antagonists exert a sufficient counter force, the head will fall forward on the cervical spine. The posterior cervical musculature has no problem maintaining balance. Mandibular postural rest position has been widely discussed in the literature in relation to the head posture. Brill et al. have stated that postural rest position will alter with changes in head position. The muscles of mastication and postural position, have been found to be affected by head positon. Rocabado states that the need for maintenance of the horizontal line of vision is ultimately of prime importance, i.e. vertical axis rotation of the head position. In the presence of normal cranio-cervical posture, the bipupilar, otic, and transverse occlusal planes should be all horizontal and parallel to one another. 9 One eye is usually dominant over the other eye and may affect the horizontal rotation of the head. Natural head position as defined by Broca is when a man is standing with his visual axis horizontal. In order to maintain the horizontal vision it is suspected that compensatory postural accommodations may occur and driven by the dominant eye. In 1993 White suggested Mandibular deviations in TMD and non-TMD groups related to eye dominance and head posture