Effect of experimental chewing on masticatory muscle pain onset.

OBJECTIVES: To evaluate the effect of a chewing exercise on pain intensity and pressure-pain threshold in patients with myofascial pain. METHODS: Twenty-nine consecutive women diagnosed with myofascial pain (MFP) according to the Research Diagnostic Criteria comprised the experimental group and 15 healthy age-matched female were used as controls. Subjects were asked to chew a gum stick for 9 min and to stay at rest for another 9 min afterwards. Pain intensity was rated on a visual analog scale (VAS) every 3 min. At 0, 9 and 18 min, the pressure-pain threshold (PPT) was measured bilaterally on the masseter and the anterior, medium, and posterior temporalis muscles. RESULTS: Patients with myofascial pain reported increase (76%) and no change (24%) on the pain intensity measured with the VAS. A reduction of the PPT at all muscular sites after the exercise and a non-significant recovery after rest were also observed. CONCLUSION: The following conclusions can be drawn: 1. there are at least two subtypes of patients with myofascial pain that respond differently to experimental chewing; 2. the chewing protocol had an adequate discriminative ability in distinguishing patients with myofascial pain from healthy controls.

Pressure pain threshold in the detection of masticatory myofascial pain: an algometer-based study.

AIMS: To compare pressure pain threshold (PPT) values for masticatory muscles in patients with signs and symptoms of myofascial pain and in asymptomatic individuals. METHODS: Fifty women with masticatory myofascial pain comprised the symptomatic group (group 1), while 49 TMD symptom-free women were selected as controls (group 2). The PPT was obtained with the aid of an algometer by applying pressure to the masseter and to the anterior, middle, and posterior temporalis. A 90.8% specificity value was used to determine the appropriate PPT cutoff values for all 4 muscles studied. Receiver operator characteristic (ROC) curve areas and the likelihood ratio (LR) were also evaluated. RESULTS: The 3-way ANCOVA test (group, muscle, and side) revealed a significantly lower PPT for all muscles in the symptomatic group (P < .001). The lowest overall PPT was found for the masseter muscle, followed by the anterior, middle, and posterior temporalis (P < .001). The 90.8% specificity was obtained with PPT values of 1.5 kgf/cm2 for the masseter, 2.47 kgf/cm2 for the anterior temporalis, 2.75 kgf/cm2 for the middle temporalis, and 2.77 kgf/cm2 for the posterior temporalis. The anterior temporalis had the highest LR. ROC curve areas of 0.84, 0.92, 0.90, and 0.90 were obtained for the masseter, anterior, middle, and posterior temporalis, respectively. CONCLUSION: The masseter and temporalis muscles require different pressures for distinguishing masticatory myofascial pain patients from asymptomatic individuals. Because the highest sensitivity (77%) and LR were found for the anterior temporalis, this muscle was considered to have the most suitable discriminative capacity.