Occlusion factors influencing the magnitude of sleep bruxism activity.

The biomechanical load during strong bruxism activity reportedly causes many dental/oral problems. However, it is unknown whether the magnitude of muscle activity during sleep is controllable. In this study, the relationship between the magnitude of muscle activity during sleep and types of tooth contacts was examined, including anterior and posterior guidance, in order to clarify how occlusion factors contribute to sleep bruxism (SB). An EMG-2-axis accelerometer system was used for monitoring patterns and activities of SB. Bruxchecker was used to evaluate tooth contacts during SB, and a condylograph was used to measure posterior guidance (sagittal condylar inclination). Results show that grinding rather than clenching or tapping was observed in the high SB group, and there was Incisor-Canine-Premolar-Molar (ICPM) tooth contact during SB grinding movement. The canine occlusal guidance (COG) was flatter in the low SB group than in the moderate SB group. Relative canine occlusal guidance (rCOG), which is the difference between the sagittal condylar inclination (SCI) and COG, was larger in the low SB group than that in the high SB group. These findings suggest that the grinding pattern must be controlled to prevent strong bruxism, and that the muscle activity during bruxism can be reduced by controlling the tooth contact pattern during SB grinding.