Publications

Myoton Clarification Note: A Guide to Interpreting the Inverse Relationship Between Logarithmic Decrement and Tissue Elasticity

Objectives: Malocclusion and occlusal wear are identified as potential risk factors for altered masticatory muscle function, pain, and temporomandibular joint (TMJ) dysfunction. This study aimed to assess the correlation between occlusal discrepancies, viscoelastic properties, and pain scores in the muscles of mastication—temporalis, masseter, pterygoids, and sternocleidomastoid muscles—in individuals with and without head and neck pain (HNP).

Methods: This pilot exploratory study included 38 participants (10 men and 28 women) divided into 18 patients without HNP (control) and 20 with HNP (case). The following parameters were assessed: severity of tooth wear by the “Individual (personal) Tooth-Wear Index” by Ekfeldt et al. (1990); viscoelastic properties (tone, stiffness, and elasticity) of masticatory muscles (masseter, temporalis, sternocleidomastoid, lateral pterygoids, and medial pterygoid muscles) using MyotonPRO; and pain scores using the numeric rating scale. Stress and anxiety were assessed using the perceived stress scale (PSS) and the Hamilton anxiety (HAM-A) scale, respectively. Correlation analyses between occlusal wear and viscoelastic properties of each muscle of mastication were conducted using Pearson’s correlation coefficient. For all analyses, statistical significance was set at p  < 0.05.

Results: Participants with HNP exhibited greater mean occlusal wear (8.417 ± 4.54) than those without HNP (6.626 ± 3.72). The frequency and stiffness of the masseter and sternocleidomastoid muscles were significantly greater in individuals with HNP. Pain scores for the muscles of mastication were higher in patients with HNP than in those without HNP. The average pain scores in the muscles of mastication were notably higher in those with HNP (mean = 5.9) than in those without HNP (mean = 3.2). The relaxation time and creep were also reduced in the masticatory muscles of patients with HNP. However, no correlation was observed between masticatory muscle pain and occlusal wear.

Conclusion: Stiffness and relaxation time in the masticatory muscles were greater in individuals with HNP. Occlusal wear affects the viscoelastic properties (tone, relaxation, and stiffness) of the masticatory muscles and is positively correlated with HNP. A multidisciplinary approach involving dentists, neurologists, and physiotherapists is essential for effectively managing patients presenting with headaches, occlusal discrepancies, muscle dysfunction, and craniofacial pain.

Keywords: anxiety, headache, muscle of mastication, occlusal wear, occlusion, orofacial pain, stress

Within the limitations of this pilot cross-sectional study, participants with greater occlusal wear demonstrated altered viscoelastic properties of selected masticatory and cervical muscles and reported a higher frequency of HNP symptoms. Those with HNP had higher stress and anxiety scores than those without HNP. Although significant differences in muscle properties were observed between groups with varying degrees of occlusal wear, no statistically significant correlations were identified between occlusal wear scores and the measured viscoelastic parameters. These findings suggest a potential link exists between occlusal wear, muscle characteristics, and pain-related outcomes; however, based on our results, causality cannot be inferred. Further large-scale longitudinal studies with more diverse populations are required to confirm these observations. However, the assessment of occlusion, TMJ, and masticatory muscle function for all patients presenting with HNP will provide a more holistic and effective management of symptoms. These findings, although they emphasize the need to evaluate occlusal wear patterns and masticatory muscle function in patients with HNP, must be weighed with caution due small sample size. Additionally, a collaborative multidisciplinary approach involving dentists, neurologists, and physiotherapists and conducting more intervention studies in this regard are essential to effectively build a stronger association and manage the complex interplay between occlusion, muscle dysfunction, and headache/neck pain.