Stress-related electromyographic responses in patients with chronic temporomandibular pain

Surface electromyographic (EMG) recordings from the right and left masseter and the left biceps muscle during stress and non-stress imagery were obtained from patients with temporomandibular myofascial pain and dysfunction syndrome (MPDS), temporomandibular joint disorder (TMJD), chronic low back pain (CBP) and healthy controls (HC). Both the MPDS and the TMJD groups displayed significantly more masseter EMG reactivity to the stressful imagery than the CBP and HC groups. The 2 dental groups did not differ significantly from each other. The MPDS patients indicated more life stress and gave higher aversiveness ratings during the experiment. These findings are discussed with respect to the validity of the TMJD and MPDS distinction.