Validity of clinical diagnostic criteria for sleep bruxism by comparison with a reference standard using masseteric electromyogram obtained with an ultraminiature electromyographic device

Actual state of the diurnal masseteric electromyogram: Differences between awareness and non-awareness of awake bruxism

PURPOSE

This study aimed to elucidate the relationship between diurnal masseter muscle activity and awareness of diurnal awake bruxism (d-AB) by conducting a comparative analysis of electromyographic (EMG) data from individuals with and without awareness of diurnal awake bruxism (d-AB), utilizing EMG data gathered from multiple subjects.

METHODS

Unilateral masseter electromyography (EMG) recordings were performed during the daytime using an ultraminiature wearable EMG device. A total of 119 participants (59 with awareness of diurnal tooth clenching [d-TC] and 60 without awareness of d-TC) were included. Waveforms longer than 0.25 s with the two amplitude conditions, exceeding twice the baseline and >5% of maximum voluntary clenching, were extracted. In addition, the number of bursts and episodes (groups of bursts), burst duration, and burst peak amplitude were calculated for each participant.

RESULTS

There were no significant differences in the EMG parameters between the groups with and without awareness of d-TC. Additionally, the frequency distribution of the number of EMG waveforms exhibited wide ranges and substantial overlap between the two groups.

CONCLUSIONS

The variability in the number of bursts and episodes, burst peak amplitude, and burst duration among subjects suggests the need for an objective classification of d-AB severity based on EMG values. The absence of significant differences and large overlap in frequency distributions between the groups with and without awareness of d-TC indicate difficulty in predicting muscle activity solely based on awareness of d-AB.

Examination of the relationship between masseter muscle activity during sleep and wakefulness measured by using a wearable electromyographic device

Purpose This study aimed to measure masseter muscle activity throughout the day in outpatients suspected of having awake bruxism (AB) and/or sleep bruxism (SB) and examine the relationship between AB and SB by comparing muscle activity during daytime wakefulness and nighttime sleep.Methods Fifty outpatients with suspected SB and/or AB participated in this study. A single-channel wearable electromyogram (EMG) device was used for EMG recording. The selected EMG bursts were divided into bursts during sleep (S-bursts) and bursts during awake state (A-bursts). The number of bursts per hour, average burst duration, and ratio of burst peak value to maximum voluntary contraction were calculated for both the S- and A-bursts. These values of the S- and A-bursts were then compared, and the correlations between them were analyzed. Additionally, the ratios of phasic and tonic bursts in the S- and A-bursts were compared.Results The number of bursts per hour was significantly higher for A-bursts than for S-bursts. No significant correlation was found between the numbers of S- and A-bursts. The ratio of phasic bursts was large and that of tonic bursts was small in both the S- and A-bursts. A comparison of the S- and A-bursts showed that the S-bursts had a significantly lower ratio of phasic bursts and higher ratio of tonic bursts than the A-bursts.Conclusions The number of masseteric EMG bursts during wakefulness did not show any association with that during sleep. It became clear that sustained muscle activity was not dominant in AB.

Accuracy of optical interocclusal registration using an intraoral scanner

PURPOSE

This study aimed to clarify the effect of occlusal force on appropriate optical interocclusal registration in clinical practice, considering periodontal ligament and jawbone deformation.

METHODS

Forty participants with natural, healthy dentition were enrolled (19 men and 21 women; mean age, 27.7 ± 2.0 years). A TRIOS3 intraoral scanner was used to scan the right lateral first premolar to the second molar areas of the upper and lower jaws. During scanning for interocclusal registration, participants were instructed to "bite normally," "bite lightly," and "bite strongly" to obtain data for the three occlusal patterns. The standard triangulated language (STL) data for each occlusion condition were superimposed using the appropriate software, following which the tooth displacement was calculated. The conventional method was also used to record the occlusal contact area for a silicone model using a dental contact analyzer.

RESULTS

Tooth displacement was significantly lower for the strong-bite condition than for the weak-bite condition (0.018 mm vs. 0.028 mm, P<0.05). As the occlusal force increased, the occlusal contact area also increased, and significant differences were observed among the different occlusal conditions (P<0.05).

CONCLUSIONS

Occlusal contact area changed depending on the bite force when using the silicone impression or optical intraoral scanning methods. Moreover, using optical impression methods in "strong bite force" may reduce the deviation and allow for stable interocclusal registration.