Orthodontic Implications of Growth and Differently Enabled Mandibular Movements for the Temporomandibular Joint

Differently enabled functional movements of the mandible and different types of maxillomandibular and occlusal relations may share a cause-and-effect relationship with the disorders affecting the temporomandibular joint (TMJ). The purpose of this article is to draw inferences with orthodontic implications for the TMJ from an overview of adverse factors for growth and biomechanics of the TMJ, dentofacial characteristics associated with temporomandibular disorders, and mechanism of action of orthodontic interventions affecting the TMJ. Inferences drawn include the importance of history taking, functional evaluation and the need for radiological evaluation of TMJ condyle and disk, and position and function during procedures that are expected to interfere with TMJ homeostasis, for example, surgical craniofacial corrective procedures, functional therapy, and occlusal reconstructive procedures. Extremes of form (eg, excessive overjet and overbite, open bite and deep bite, skeletal hyperdivergence and hypodivergence) and differently enabled mandibular functions resulting in overloading of TMJs are all potential factors in the etiology of its disorders, thus enhancing the need for its evaluation before, during, and after treatment; a reciprocal relationship exists between growth and biomechanics of the TMJ, dentofacial characteristics and articular afflictions, occlusion and TMJ, and mandibular movements and TMJ. These interrelated, interdependent, and/or coexistent factors have a bearing on the diagnosis and treatment of the disorders of the TMJ. Orthodontic therapy should be directed to achieve a structural balance to facilitate physiologic adaptation and rehabilitation. Because the movements of the mandible are not restricted by the joint structure per se, other operative templates, for example, neuromuscular and psychological, apart from the structural template, contribute significantly to its complex functions and pathology. There is a need to find optimum values of structure and function of the masticatory system and develop mechanisms that can record and reproduce highly accurate geometric models of a subject's TMJ and teeth combined with recordings of chewing trajectories and 3-dimensional TMJ movements to obtain subject-specific models of masticatory system by either improving upon conventional mechanical articulators or by application of virtual-reality techniques for the development of virtual articulators for diagnosis and treatment of the disorders of masticatory system.