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. Keywords: masticatory muscle, myofascial pain, pressure pain threshold, sensitivity, specificity, temporalis muscle