Search

Background: 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., Objectives: 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., Methods: 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., Results: 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., Conclusion: 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., (© 2024 The Author(s). Journal of Oral Rehabilitation published by John Wiley & Sons Ltd.)

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., (© 2023 John Wiley & Sons Ltd.)