title: Experimental low-level jaw clenching inhibits temporal summation evoked by electrical stimulation in healthy human volunteers.
abstract: OBJECTIVE
  To examine the effect of low-level jaw clenching on temporal summation in healthy volunteers.
  
  
  METHODS
  In 18 healthy volunteers, the pain intensities evoked at the masseter muscle and the hand palm by the first and last stimuli in a train of repeated electrical stimuli (0.3 or 2.0 Hz) were rated using 0-100mm visual analogue scales (VAS), in order to evaluate temporal summation before and after three types of jaw-muscle tasks: low-level jaw clenching, repetitive gum chewing and mandibular rest position. A set of concentric surface electrodes with different diameters (small and large) was used for the electrical stimulation.
  
  
  RESULTS
  The temporal summation evoked by the large diameter electrode with 2.0 Hz stimulation decreased significantly both on the masseter and the hand after low-level clenching (P ≤ 0.03), but did not show any significant change after the other tasks (P > 0.23). The VAS score of the first stimulation did not show any significant changes after low-level clenching (P > 0.57).
  
  
  CONCLUSIONS
  Experimental low-level jaw clenching can inhibit pain sensitivity, especially temporal summation. Low-level jaw clenching can modify pain sensitivity, most likely through the central nervous system. The findings suggest that potential harmful low-level jaw clenching or tooth contacting could continue despite painful symptoms, e.g., temporomandibular disorders.
authors.affiliation: Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan. Electronic address: dm09119f@cc.nagasaki-u.ac.jp.
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Tada
authors.affiliation: Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan. Electronic address: torisu@nagasaki-u.ac.jp.
authors.forename: Tetsurou
authors.initials: T
authors.lastname: Torisu
authors.affiliation: Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan. Electronic address: mihobonn@nagasaki-u.ac.jp.
authors.forename: Mihoko
authors.initials: M
authors.lastname: Tanaka
authors.affiliation: Department of Prosthetic Dentistry, Graduate School of Biomedical Sciences, Nagasaki University, Sakamoto 1-7-1, Nagasaki 852-8588, Japan. Electronic address: hmurata@nagasaki-u.ac.jp.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Murata
authors.affiliation: Department of Oral Health Sciences, KU Leuven, Belgium; Dentistry, University Hospitals Leuven, Kapucijnenvoer, B-3000 Leuven, Belgium. Electronic address: antoon.delaat@uzleuven.be.
authors.forename: Antoon
authors.initials: A
authors.lastname: De Laat
authors.affiliation: Section of Clinical Oral Physiology, School of Dentistry, Aarhus University, Aarhus, Denmark; Scandinavian Center for Orofacial Neurosciences (SCON), Vennelyst Boulevard 9, 8000 Aarhus C, Denmark; Department of Dental Medicine, Karolinska Institutet, Huddinge, Sweden. Electronic address: peter.svensson@odont.au.dk.
authors.forename: Peter
authors.initials: P
authors.lastname: Svensson
mesh_terms: D000328:Adult; D004558:Electric Stimulation; D004576:Electromyography; D005157:Facial Pain / Q000209:etiology; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D007568:Jaw / Q000502:physiology*; D008297:Male; D008406:Masseter Muscle / Q000502:physiology*; D009119:Muscle Contraction / Q000502:physiology*; D010147:Pain Measurement; D017288:Pain Threshold / Q000502:physiology
keywords: Concentric electrode; Masticatory muscles; Pain sensitivity; Stimulation depth; Temporal summation; Temporomandibular disorders