Aims: The purpose of this study was to evaluate the degree of the mastication predominance of edentulous individuals with complete dentures by comparing with healthy dentate, and bilateral and unilateral posterior missing teeth subjects using electromyogramphic (EMG) analysis and visual analogue scale (VAS).

Methods: Twenty-five edentulous individuals with complete dentures were instructed to chew on the right side and then on the left side, and EMG activity of the bilateral masseter muscles was recorded simultaneously. The Concordance rates between instructed and judged chewing sides were calculated. Then, 30 healthy dentate subjects, 19 bilateral posterior missing teeth subjects, 30 unilateral posterior missing teeth subjects, and 25 edentulous subjects were instructed to freely chew three kinds of test foods (chewing gum, peanuts, and gummy jellies). In each trial, EMG activities were recorded from bilateral masseter muscles and the mastication predominant index (MPI) was calculated. Self-awareness of mastication predominance (SAMP) was evaluated by using a modified visual analogue scale. The data were compared in all subject groups.

Results: Concordance rate—the percentage of events (chewing cycles) where the instructed chewing side coincided with the chewing side, as judged by EMG analysis—was >93% for all test foods among complete denture wearers. The MPIs of the edentulous group for each test food were as follows: peanuts 68.4%, gummy jellies 50.0%, and chewing gum 47.4%. Statistical analyses showed no significant difference in MPI between edentulous and the other three groups. In edentulous group, there was significant correlations between SAMP and mastication predominance score (MPS) in chewing gum.

Conclusion: Our analysis suggests that chewing side evaluation of edentulous subjects with EMG was effective to reveal mastication predominance.

Sleep bruxism (SB) is a type of sleep disorder. Because pharmacotherapy for sleep disorders (sleeping drugs, antidepressants etc.) is associated with strong side effects, a complementary therapy in the form of olfactory stimulation with aromas was focused on. The purpose of this study was to investigate how olfactory stimulation with aromas affects SB. The subjects were 26 healthy, dentulous individuals (male: 21, female: 5, mean age: 24.8±3.2 years). Before starting the experiment, SB was confirmed in all 26 subjects using polysomnography (PSG) during nighttime sleep. Lavender (LA) was used for olfactory stimulation, and deionized water was used as the control (CO). The 26 subjects were randomly divided into the LA group and the CO group, and a crossover test, in which olfactory stimulation alternatingly administered, was performed. To eliminate the influence of initial night effects and obtain baseline data, PSG and masseter electromyography (EMG) measurements were performed using a portable high-precision EMG device on three consecutive nights. When crossing over, to eliminate any carry-over effects of each condition, the olfactory stimulation type was switched after a 1-week washout period, and PSG and EMG measurements were performed in the same manner over two consecutive nights. Sleep variables were evaluated with PSG analysis, and the number of SB events was calculated based on masseter EMG analysis. This resulted in the following conclusions.

1. Olfactory stimulation with LA improved the sleep state significantly for five of six sleep variables.

2. As compared to the baseline and the CO group, the number of SB events in the LA group decreased significantly.

3. Results suggested that olfactory stimulation using LA may reduce the number of SB events regardless of a subjective sense of favorable or poor sleep.

The results demonstrated the possibility that olfactory stimulation with applying LA improves the sleep state while reducing the number of SB events.