Laterotrusive occlusal schemes and their effect on supra- and infrahyoid electromyographic activity.

The objective of this study was to determine the effects of canine guidance and group function on supra- and infrahyoid electromyographic (EMG) activity. The sample included 40 healthy subjects, 20 with bilateral canine guidance and 20 with bilateral group function. Surface electrodes were used to record the integrated EMG (IEMG) activity of the left supra- and infrahyoid muscles during (1) grinding from intercuspal position to lateral edge-to-edge contact position (with canine guidance or group function), (2) static clenching in edge-to-edge lateral contact position with canine guidance or group function, and (3) grinding from lateral edge-to-edge contact position (with canine guidance or group function) to intercuspal position. IEMG activity in the suprahyoid or infrahyoid muscles was not significantly different with canine guidance or group function. Supra- and infrahyoid IEMG activity in condition 2 was significantly higher than in condition 3, which was significantly higher than in condition 1. Supra- and infrahyoid IEMG activity was not significantly different with canine guidance and group function. Supra- and infrahyoid IEMG activity during the static recording (clenching) was significantly higher than during the dynamic recordings (grinding). Activity during grinding from the lateral edge-to-edge contact position to the intercuspal position was higher than vice versa.