Reliability of Mechanical Sensitivity Mapping in the Orofacial Region of Healthy Chinese Individuals: Towards Standardized Assessment of Somatosensory Function

Aims: To investigate the test-retest reliability of mechanical sensitivity mapping in the masseter and temporomandibular joint (TMJ) regions between sessions, days, and examiners with a fixed and standardized pressure stimulus, as well as to compare mechanical sensitivity between sides and sites. Methods: A total of 20 healthy young volunteers participated. Pressure stimulation was applied to 15 sites in the masseter region with a Palpeter device of 1.0-kg force and to 9 sites in the TMJ region with a Palpeter of 0.5-kg force. All participants were tested twice in two separate sessions on the same day by Examiner 1 with an interval of 3 hours between tests. After 1 week, the protocol was repeated in the same manner in two separate sessions by Examiner 1 and Examiner 2 (one session each). Results: Analysis of variance (ANOVA) of numeric rating scale (NRS) scores and center of gravity (COG) values in both regions showed no significant main effects of examiner, day, or session (P ≥ .167). The test-retest reliability of data implied excellent agreement (intra-class correlation coefficients all > 0.75) between different examiners, days, and sessions. In addition, the ANOVA of the mean NRS scores in both regions showed significant main effects of site (P = .001). Conclusion: This feasible and reliable technique may provide a new tool for comprehensive evaluation of mechanical allodynia and hyperalgesia in the orofacial region, which are common features related to temporomandibular disorders and other chronic craniofacial pain conditions. Keywords: mechanical sensitivity mapping, numeric rating scale, palpometer, reliability, trigeminal pain physiology