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ABSTRACT Background Objectives Methods Results Conclusion Intra‐oesophageal acid stimulation increases masseter muscle activity. However, the infusion speeds used in previous studies are significantly slow, with minimal acid volume (30 mL over 30 min). Additionally, it is unclear how masseter muscle activity, symptoms of discomfort, stress levels and saliva quantity change over time.The time course of masseter muscle activity, heartburn and discomfort symptoms, salivary cortisol concentration to assess stress, autonomic nervous system (ANS) activity and saliva quantity under the influence of intra‐oesophageal acid infusion were evaluated at a faster injection rate and larger volume than in previous studies.Ten healthy adults underwent polygraphic monitoring, consisting of electromyography of the masseter muscle and electrocardiography during intra‐oesophageal acid infusion (10 mL/min, 10 min). Symptoms of heartburn and discomfort were assessed using the visual analogue scale (VAS), and saliva quantity was measured. Friedman's test was used for multiple comparisons.Masseter muscle activity, VAS scores for heartburn and discomfort, as well as saliva quantity during the 10‐min acid infusion, increased significantly compared with that before acid infusion (p < 0.001, 0.001, 0.019 and 0.047, respectively) and decreased 10 and 20 min after acid infusion (p = 0.004, 0.004 and 0.007, respectively). No significant changes were observed in the salivary cortisol concentration or ANS activity.Intra‐oesophageal acid infusion stimulated symptoms of heartburn and discomfort and increased masseter muscle activity and saliva production, which may not be related to psychological stress. [ABSTRACT FROM AUTHOR]

Background: Masseter muscle activity during wakefulness may be associated with temporomandibular disorder (TMD)‐related symptoms, psychosocial status and pain‐related disability; however, this relationship is unclear. Objectives: This study aimed to determine the relationship between masseter muscle electromyography (EMG) burst/duration during wakefulness and TMD‐related symptoms, psychosocial status and pain‐related disability. Methods: Sixty participants were assessed masseter muscle activity during wakefulness using a data‐logger‐type ultraminiature EMG system and TMD‐related symptoms, psychosocial status and pain‐related disability through Axis I and II of the diagnostic criteria for TMD (DC/TMD). EMG bursts lasting longer than 0.25 s but less than 2.0 s and those lasting longer than 2.0 s were classified as phasic and tonic bursts, respectively. Results: Participants with palpation‐related pain in the temporalis and masseter muscles, as assessed through the DC/TMD examination form in Axis I, had more bursts (number/h) (p =.035 and p =.009, respectively) and longer duration (time/h) (p =.013 and p =.004, respectively) of tonic bursts of the masseter muscle during wakefulness. Participants with palpation‐related pain in the masseter muscles had higher oral behaviour scores during wakefulness using Axis II (p =.001), which affected the number and duration of tonic bursts of the masseter muscle activity during wakefulness (p =.011 and p =.007, respectively). Conclusion: As tonic bursts mainly reflect clenching, individuals with pain in the masseter muscles by palpation may have a high frequency and longer duration of clenching, as well as a high frequency of oral behaviours during wakefulness. [ABSTRACT FROM AUTHOR]

To evaluate miniscrew stability and perform a histomorphometric analysis of the bone around the miniscrew under a load corresponding to orthopedic force. Thirty-two miniscrews were implanted into eight rabbit tibias. Auxiliary group rabbits received auxiliary devices with miniscrews (n = 8, 28 days; n = 8, 56 days), and those in the nonauxiliary control group received miniscrews without auxiliary devices (n = 8, 28 days; n = 8, 56 days). Elastics were placed between miniscrews to apply a load of 5 N. Miniscrew stability was evaluated using a Periotest. Bone-to-implant contact (BIC) and spike implantation depth were measured histomorphologically. Periotest values in the auxiliary group were significantly lower than those in the nonauxiliary group at all time periods. There was no significant difference in BIC between the auxiliary and nonauxiliary groups at 28 or 56 days postimplantation. The implantation spike depth in the auxiliary group was significantly greater at 56 days compared to that at 28 days. Newly formed bone was observed around the spike of the auxiliary device at 56 days. The results suggest that the use of miniscrews in conjunction with auxiliary devices provides stable skeletal anchorage, which may be useful in orthopedic treatments. [ABSTRACT FROM AUTHOR]

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.