Occlusal interferences and mastication: An electromyographic study

Abstract

T I n spite of the many recent advances toward a better understanding of the neurologic aspects of mastication, the function of tooth contacts as a part of the neuromuscular mechanisms of chewing is still a rather controversial question. Some investigators attribute no functional importance to tooth contacts during chewing.’ However, others see a justification for the equilibration of occlusal disharmonies in the fact that tooth contacts occur during mastication.” The neurophysiologic basis by which occlusal disharmonies might act in the creation of occlusal trauma is connected with the possible role of tooth contacts and tooth sliding during functional or dysfunctional movements. Karolyi” recognized early the important role of bruxism in the etiology of periodontal disease and also the interrelationship between occlusal disharmonies and bruxism itself. Thielemann, 4 in discussing the etiology of periodontal disease, clearly distinguishes between chewing and “empty” grinding movernents. Drum” first stressed, in the European literature, the difference between the self-protecting functional movements during mastication and the auto-destructive ‘~I)arafurlctionst“ like bruxism, which are performed on a subconscious level. This view was also cxpressed earlier in the American literature by Shanahan’ and Jankelson.’ Electromyclgraphic (EMG) studies by Ramfjord, fi in an evaluation of the effect of occlusal interferences on bruxism and the EMG activity of the chewing muscles, showed that the masticatory movements were unreliable as an indicator of occlusal interferences for patients who manifested marked EMG changes during “empty” man-