Anterior guidance: its effect on electromyographic activity of the temporal and masseter muscles.

I n his classic article D’Amico’ states: “When the canines are in normal interlocking position, the lateral and forward movement is limited so that when an attempt is made to move the mandible laterally or forward, there is an involuntary reaction when the canines comein contact. The reaction is an immediate break in the tension of the temporal and masseter muscles, thus reducing the magnitude of the applied force. Regardless of how hard the individual tries to tense these muscles, as long as the canines are in contact, it is impossible for these muscles to assume full tension.” He continues: “The length of the roots of the canines and the anatomical structure of the supporting alveolar process gives testimony to nature’s intention as to the function intended. What may appear as trauma as they come in contact is not trauma at all, because when contact is made, muscular tension is involuntarily reduced, thus reducing the magnitude of applied force.” The purpose of our study was to determine the effect of two occlusal schemes on the temporal and masseter muscles. The first occlusal scheme used anterior guidance to eliminate all contact of posterior teeth in eccentric movements. The second occlusal scheme allowed selective posterior occlusal contact in eccentric movements. These occlusal schemes were developed using maxillary occlusal splints. In addition, it was desired to determine if the contact of the canines or the elimination of posterior tooth contacts reduced muscle tension.