The interdisciplinary approach to the assessment of mechanical pain sensitivity in temporomandibular disorders

Introduction: Temporomandibular disorders (TMDs) are non-dental orofacial pain conditions with a high prevalence in the general population (5-12%). One of the clinical peculiarities is the fact that TMD is often associated with various changes in mechanical pain sensitivity (MPS) at the level of the structures of the stomatognathic system (temporomandibular joint, masticatory muscles), which has the impact of increasing the difficulties of diagnosing this problem for the clinicians. Objective of the study: to evaluate options for clinical investigation of the expression and spatial distribution of mechanical pain sensitivity (MPS) in temporomandibular disorders. Material and methods: We performed the analysis of the variation in the expression of mechanical pain sensitivity (MPS) based on the data obtained by algometry (thresholds of sensitivity/tolerance to pressure) collected in 55 patients. The investigation was carried out in the projection of acupuncture points ST6 (masseter muscle), ST7 (temporomandibular joint). Data collection was carried out in 2 states (relative rest conditions, operational stress modeling). The investigation of the spatial distribution of mechanical pain sensitivity (MPS) was carried out through pain maps at the level of the masseter muscle (30 patients with temporomandibular disorders and 30 asymptomatic people - control group). Results: In the study, it was identified that the expression of mechanical pain sensitivity (MPS) varies according to the test conditions (relative rest/modeled operational stress), being attested statistically significant reductions at the masseter muscle level (tolerance threshold and sensitivity/tolerance threshold ratio) under stress conditions. This state reveals a hypoalgesia occurring after the stressful event, which reflects the complexity of the mechanisms involved in the pathogenesis and evolution of TMD. The observed spatial distribution of mechanical pain sensitivity (MPS) revealed the importance of using complex synthetic indices, which allow the processing of raw data (sensitivity/tolerance thresholds), including the reflection at the level of MPS heterogeneity/homogeneity. Conclusions: Investigating the particularities of mechanical pain sensitivity at the level of the stomatognathic structure, especially masticatory muscles in temporomandibular disorders, which represent a reliable interdisciplinary approach, which requires investigation in multiple standardized conditions (relative comfort/operational stress modeling), with the evaluation of the sensitivity distribution (pain maps). The integral view of TMD through the prism of MPS aspects provides new clinical evaluation criteria (expression intensity, spatial distribution, heterogeneity).