Observation of Consecutive Muscle Activity of Sleep Bruxism Individuals

Objectives: Consecutive muscle activity of sleep bruxism over a period is not clearly observed. This study consecutively observed the muscle activity of sleep bruxism (SB) individuals using Stabilization Splint (SS) for 28 days.

Methods: Seven SB patients (4 males and 3 females, with a mean age 27.0 years) were recruited for this study. SS was fabricated by using auto-polymerized resin, covering the occlusal surface of the maxillary dental arch. SS had smooth surface with 2 mm thickness in second molar regions, and occlusal contacts with mandibular buccal cusps. A portable Electromyography (EMG) was used and recorded maximal voluntary contraction (MVC), grinding, tapping, coughing, and swallowing, on one side of superficial masseter muscle.
Three consecutive nights of masseter muscle activities (pre SS) followed by 28 consecutive night of masseter muscle activities with SS were inserted (post SS). Phasic and tonic activities above 20% MVC were detected as a SB activity. Other muscle activities such as coughing or swallowing were eliminated from the obtained EMG. The total duration of nocturnal masseter EMG per hour of sleep (DURATION) were compared between pre SS and post SS.

Results: Among all subjects, one subject post-SS DURATION did not exceed the pre-SS DURATION. However, flexible change on daily basis and fluctuation during night was observed. Coefficient of variation (CV) on 28 nights was 103％ for tonic and 106％ for phasic.
Another subjects showed decrease of post SS DURATION of both phasic and tonic on first two days, and the DURATION was increased from day 3. CV was 60% for tonic and 189% for phasic.

Conclusions: Observation of consecutive muscle activity has benefit for the subjects because there is fluctuation during night, since it is not enough to measure the muscle activity for only 1-2 night.