Referred Pain and Sensations Evoked by Standardized Palpation of the Masseter Muscle in Healthy Participants

Aims: To determine if standardized palpation of the masseter muscle can evoke referred pain and/or sensations in healthy individuals and to compare the mechanical sensitivities in response to three different levels of palpation force. Methods: A total of 32 pain-free individuals participated. The right masseter muscle was divided into 15 test sites. Mechanical sensitivity of the masseter was assessed with three mechanical stimuli (0.5 kg, 1.0 kg, or 2.0 kg) applied by palpometers to the 15 test sites for 5 seconds each site. Participants scored the perceived intensity of pain and unpleasantness of each of the three mechanical stimuli on 0-100 numeric rating scales (NRS). After each stimulus, the duration of aftersensation was measured, and the participants were also asked to indicate areas within the orofacial region with referred pain/sensations. Data were tested using analysis of variance, Tukey post hoc, and McNemar's tests with a 5% level of significance. Results: Referred pain/sensations were most commonly evoked with the 2.0-kg stimulus (34.4% of participants; P < .05) compared to the 1.0-kg (12.5%) and 0.5-kg stimuli (3.1%). There were significant effects of stimulus intensity on NRS scores for pain and unpleasantness, as well as for aftersensation (P < .05). There were significant effects on NRS scores for pain and unpleasantness for the 1.0- and 2.0-kg stimuli (P < .05) and on aftersensation for the 2.0-kg stimulus (P < .05). Conclusion: These results indicate that referred pain/sensations in the orofacial region are frequent phenomena among healthy individuals during standardized palpation of the masseter muscle.