• Yuanxiu Zhang, Sheng Shao, Jinglu Zhang, Lin Wang, Kelun Wang, and Peter Svensson.
• aJiangsu Key Laboratory of Oral Diseases, Nanjing Medical University, Nanjing, China bDepartment of Orthodontics, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing, China cOrofacial Pain and TMD Research Unit, Institute of Stomatology, Affiliated Hospital of Stomatology, Nanjing Medical University, Nanjing, China dCenter for Sensory-Motor Interaction (SMI), Department of Health Science & Technology, Aalborg University, Aalborg, Denmark eSection of Orofacial Pain and Jaw Function, Department of Dentistry and Oral Health, Aarhus University, Aarhus, Denmark fDepartment of Dental Medicine, Karolinska Institutet, Huddinge, Sweden gScandinavian Center for Orofacial Neurosciences (SCON).
• Pain. 2017 Jul 1; 158 (7): 1272-1279.

AbstractTemporal summation of nociceptive inputs may be an important pathophysiological mechanism in temporomandibular disorders (TMD) pain; however, it remains unknown how natural jaw function relates to underlying pain mechanisms. This study evaluated changes in pain and movement patterns during repeated jaw movements in patients with painful temporomandibular joints (TMJ) compared with healthy controls. Twenty patients with TMD with TMJ pain, and an anterior disk displacement without reduction and 20 age- and gender-matched healthy volunteers were included. Participants performed 20 trials (4 × 5 sessions) of standardized and repeated mandibular movements, and scored the movement-associated pain intensity on 0 to 10 numeric rating scale in addition to measurements of jaw movements. Patients with TMJ pain reported higher baseline pain compared to the control group for all types of jaw movements (P = 0.001) and significant increases in numeric rating scale pain scores by repetition of jaw movements (P < 0.001), which was not observed in the control group (P > 0.05). Jaw total opening distance (P = 0.030), maximum opening velocity (P = 0.043) and average closing velocity (P = 0.044) in the TMJ pain group were significantly reduced during the repeated movements. In the control group, however, total opening distance (P = 0.499), maximum opening velocity (P = 0.064), and average closing velocity (P = 0.261) remained unchanged, whereas average opening velocity (P = 0.040) and maximum closing velocity (P = 0.039) increased. The study demonstrates that repeated jaw movements constitute a sufficient and adequate stimulation for triggering temporal summation effects associated with significant inhibition of motor function in painful TMJs. These findings have practical implications for diagnosis of TMD pain and for more mechanism-driven management protocols in the future.

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