title: The effects of capsaicin-induced intraoral mucosal pain on jaw movements in humans.
abstract: OBJECTIVE
  To determine whether mucosal pain, evoked through a novel topical capsaicin model, has an effect on jaw movement and whether psychologic factors have an association with any pain-induced movement effects.
  
  
  METHODS
  Mandibular movement was recorded from 26 asymptomatic subjects during free opening and closing, resistant opening jaw movements, and free and standardized chewing, at baseline and in test sessions while the subjects were wearing a custom maxillary mouthguard coated with either capsaicin cream (pain group, 13 subjects) or placebo cream (control group, an additional 13 subjects). All subjects completed the Depression Anxiety Stress Scales (DASS) and the Pain Catastrophizing Scale (PCS). Statistical analyses were made with independent t tests and bivariate correlation analyses.
  
  
  RESULTS
  Capsaicin induced moderate pain in the pain group, but there were no significant differences between the two groups in the change of kinematic variables from baseline except for a significantly greater increase from baseline in the number of chewing cycles per second (chewing rate) for free (t = 2.74, P = .011) and standardized chewing (t = 2.10, P = .047) in the pain group compared with the control group. In the pain group, the DASS anxiety score was negatively correlated (r = -.70, P = .007), with the change of mean opening velocity from the baseline to the test session in the free opening task, and the DASS depression score was negatively correlated to the increase of chewing rate in the free chewing task from the baseline to the test session (r = -.56, P = .046).
  
  
  CONCLUSIONS
  Capsaicin-induced mucosal pain resulted in a significant increase in chewing rate but had no effect on amplitude or velocity in opening/closing jaw movements and chewing. Anxiety and depression scores correlated negatively with velocity in free opening jaw movement and chewing rate, respectively.
authors.affiliation: Faculty of Dentistry, University of Sydney, Westmead, New South Wales, Australia.
authors.forename: Nan Nan
authors.initials: NN
authors.lastname: Zhao
authors.forename: Terry
authors.initials: T
authors.lastname: Whittle
authors.forename: Greg M
authors.initials: GM
authors.lastname: Murray
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Peck
mesh_terms: D061725:Accelerometry; D000222:Adaptation, Physiological; D000328:Adult; D001007:Anxiety / Q000503:physiopathology; D002211:Capsaicin / Q000494:pharmacology; D016022:Case-Control Studies; D003863:Depression / Q000503:physiopathology; D005157:Facial Pain / Q000139:chemically induced / Q000503:physiopathology*; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008297:Male; D008334:Mandible / Q000503:physiopathology*; D008409:Mastication / Q000502:physiology; D008959:Models, Neurological; D009043:Motor Activity / Q000502:physiology*; D009061:Mouth Mucosa / Q000187:drug effects*; D009068:Movement / Q000502:physiology*; D011581:Psychological Tests; D018689:Sensory System Agents / Q000494:pharmacology; D011795:Surveys and Questionnaires
chemical_list: D018689:Sensory System Agents; D002211:Capsaicin