Effects of intra‐oesophageal acid infusion and a stress task on masseter muscle activity and autonomic nervous activity in wakefulness

Abstract

Background: Gastroesophageal reflux disease may be an important risk factor for awake bruxism. Additionally, it has been known that a psychological stress task affects masseter muscle activity, and autonomic nervous system (ANS) activity modulation induces masseter muscle activity.Objectives: This study aimed to investigate whether task-induced stress and experimental oesophageal acid infusion increase masseter muscle activity and alter ANS activity, compared to rest task and oesophageal saline infusion, respectively. Methods:Polygraphic monitoring, consisting of electromyography of the masseter muscle and electrocardiography, was performed in 12 healthy adult men during 30min interventions with intra-oesophageal saline or acid infusion, while reading a book quietly, as rest, and while performing calculation, as a stress task.Results: At rest, masseter muscle activity and parasympathetic nervous system (PNS) activity during acid infusion were significantly higher (P = .019) and lower (P = .021) than during saline infusion, respectively. During saline infusion, both masseter muscle activity and sympathetic nervous system (SNS) activity or PNS activity while performing the calculation task were higher (P = .022 and .012, respectively) or lower (P = .007) than those during the reading task, respectively. In two-way repeatedmeasures ANOVA, intra-oesophageal infusion (saline or acid) significantly affected masseter muscle activity (P = .008) and PNS activity (P = .021). However, performing tasks (reading or calculation) significantly affected only PNS activity (P = .028). Conclusion:Intra-oesophageal acid infusion significantly increased masseter muscle activity and decreased PNS activity. In contrast, stress task not only significantly decreased PNS activity, but only modestly increased masseter muscle activity and SNS activity. K E Y W O R D Sacid infusion, awake bruxism, gastroesophageal reflux disease, parasympathetic nervous system, psychological stress, sympathetic nervous system

Secondary bruxism: A valid diagnosis or just a coincidental finding of additional masticatory muscle activity? A narrative review of literature

“…In the same way, the association between GERD and AB was previously verified 92 . Intra‐oesophageal acid infusion in health adult men while reading a book quietly, and while performing calculation, as a stress task, also increased masseter muscle activity 95 …”

“…92 Intra-oesophageal acid infusion in health adult men while reading a book quietly, and while performing calculation, as a stress task, also increased masseter muscle activity. 95 A narrative review suggested that tooth wear is associated with dental sleep disorders oro-facial pain, oral dryness, GERD and SB, considering that SB is indirectly associated with chemical tooth wear through GERD. 96 Regardless of this, in long-term GERD cases, SB is associated with severe dental wear.…”

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“…Regarding GERD, SB is considered a possible protective factor for the disease 11 , 14 , 17 , 18 . This hypothesis describes that interdental contact from SB would activate the mechanoreceptors of the periodontal ligament, stimulating salivary secretion and neutralizing the acidic pH of the oral cavity 11 , 14 , 17 , 18 . Polysomnographic studies that evaluated patients with sleep bruxism and GERD support this hypothesis 11 , 14 , 17 , 18 .…”

“…This hypothesis describes that interdental contact from SB would activate the mechanoreceptors of the periodontal ligament, stimulating salivary secretion and neutralizing the acidic pH of the oral cavity 11 , 14 , 17 , 18 . Polysomnographic studies that evaluated patients with sleep bruxism and GERD support this hypothesis 11 , 14 , 17 , 18 . More studies need to be carried out to establish and understand this relationship.…”