title: Pain and intramuscular release of algesic substances in the masseter muscle after experimental tooth-clenching exercises in healthy subjects.
abstract: OBJECTIVE
  To investigate whether experimental tooth clenching leads to a release of algesic substances in the masseter muscle.
  
  
  METHODS
  Thirty healthy subjects (16 females, 14 males) participated. During two sessions, separated by at least 1 week, intramuscular microdialysis was performed to collect masseter muscle 5-hydroxytryptamine (5-HT) and glutamate as well as the metabolic markers pyruvate and lactate. Two hours after the start of microdialysis, participants were randomized to a 20-min repetitive experimental tooth-clenching task (50% of maximal voluntary contraction) or a control session (no clenching). Pain and fatigue were measured throughout. The Friedman and Wilcoxon tests were used for statistical analyses.
  
  
  RESULTS
  No alterations were observed in the concentrations of 5-HT, glutamate, pyruvate, and lactate over time in the clenching or control session, or between sessions at various time points. Pain (P < .01) and fatigue (P < .01) increased significantly over time in the clenching session and were significantly higher after clenching than in the control session (P < .01).
  
  
  CONCLUSIONS
  Low levels of pain and fatigue developed with this experimental tooth-clenching model, but they were not associated with an altered release of 5-HT, glutamate, lactate, or pyruvate. More research is required to elucidate the peripheral release of algesic substances in response to tooth clenching.
authors.forename: Andreas
authors.initials: A
authors.lastname: Dawson
authors.forename: Bijar
authors.initials: B
authors.lastname: Ghafouri
authors.forename: Björn
authors.initials: B
authors.lastname: Gerdle
authors.forename: Thomas
authors.initials: T
authors.lastname: List
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
authors.forename: Malin
authors.initials: M
authors.lastname: Ernberg
mesh_terms: D000328:Adult; D001732:Bite Force; D002012:Bruxism / Q000378:metabolism; D016009:Chi-Square Distribution; D018592:Cross-Over Studies; D005157:Facial Pain / Q000378:metabolism / Q000503:physiopathology*; D005260:Female; D018698:Glutamic Acid / Q000378:metabolism; D006801:Humans; D007568:Jaw / Q000502:physiology*; D019344:Lactic Acid / Q000378:metabolism; D008297:Male; D008406:Masseter Muscle / Q000378:metabolism* / Q000502:physiology; D017551:Microdialysis; D009119:Muscle Contraction / Q000502:physiology*; D018763:Muscle Fatigue / Q000502:physiology*; D019289:Pyruvic Acid / Q000378:metabolism; D012701:Serotonin / Q000378:metabolism*; D016037:Single-Blind Method; D018709:Statistics, Nonparametric; D055815:Young Adult
chemical_list: D012701:Serotonin; D019344:Lactic Acid; D018698:Glutamic Acid; D019289:Pyruvic Acid