Hiroaki Tada1, Tetsurou Torisu2, Mihoko Tanaka3, Hiroshi Murata4, Antoon De Laat5, Peter Svensson6. 1. 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. 2. 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. 3. 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. 4. 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. 5. Department of Oral Health Sciences, KU Leuven, Belgium; Dentistry, University Hospitals Leuven, Kapucijnenvoer, B-3000 Leuven, Belgium. Electronic address: antoon.delaat@uzleuven.be. 6. 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.
Abstract
OBJECTIVE: To examine the effect of low-level jaw clenching on temporal summation in healthy volunteers. DESIGN: 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.
OBJECTIVE: To examine the effect of low-level jaw clenching on temporal summation in healthy volunteers. DESIGN: 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.