An evaluation of anterior temporal and masseter muscle activity in appliance therapy

Needle electromyography (NEMG) was used to compare the effects of the Hawley bite plane (HBP) and superior repositioning splint (SRS) on the ipsilateral masseter and anterior temporal muscles at rest and in maximum closure. Twenty adult subjects were randomly divided into two groups of 10. One group wore the HBP for 8 hours per day and the other group wore SRS for the same time period. After 2 weeks of use, NEMG was conducted on the ipsilateral masseter and temporal muscles with and without the device in place. Each group then wore the other appliance for an identical period and underwent NEMG. Both appliance designs produced decreases in electromyographic responses during use. Individuals in the HBP group showed a 48.6% decrease in anterior temporal activity and a 34.1% decrease in masseter muscle activity. The SRS group demonstrated 23.5% and 16.2% decreases in anterior temporal and masseter muscles activities, respectively. This is the first report of the use of NEMG as a mode of assessment of muscle activity in human or animal subjects.