Investigation of masticatory muscle thickness and mechanosensitivity of cervical and masticatory muscles in myofascial temporomandibular disorder patients with bruxism: A cross-sectional study

Role of the masseter, anterior temporalis, and sternocleidomastoid muscles in myofascial temporomandibular disorder pain: evaluation of thickness and stiffness by ultrasonography

OBJECTIVES

This study aimed to compare the thickness and stiffness of the masseter, anterior temporalis, and sternocleidomastoid muscles of patients diagnosed with myofascial temporomandibular disorders (TMD) pain to those of a control group.

METHODS

This was a cross-sectional study conducted at a single center. Twenty-five patients diagnosed with myofascial TMD pain and 29 asymptomatic controls (Control Group) matched by age and sex were recruited. B-mode ultrasonography and shear wave elastography were used to measure the thickness and stiffness of the bilateral masseter, temporalis, and sternocleidomastoid muscles. All measurements were performed while resting and clenching. Patients were systematically evaluated for pain intensity and maximum mouth opening.

RESULTS

There were no differences between groups in the resting and clenching thickness of any muscles (p > 0.05). There were no differences in the stiffness of the measured muscles at rest and clench between the groups, except for the masseter (p > 0.05). Individuals with myofascial TMD pain showed higher median stiffness in the right (p < 0.001) and left (p = 0.003) masseter muscles during clenching (but not during resting) compared with controls.

CONCLUSIONS

Clenching masseter stiffness was greater in individuals with myofascial TMD pain than in asymptomatic controls. These findings might help to understand the jaw biomechanics and dysfunction of individuals with myofascial TMD pain.

A new test protocol and device for measuring the cranio-cervical flexion test in participants with bruxism

Introduction

The craniocervical flexion test (CCFT) has been proposed to assess muscular stabilization using deep neck flexors. Reliability of the CCFT using a pressure biofeedback unit has been regarded as doubtful, and the level of evidence is reportedly low.The aim of the current study is to pilot test an alternative measurement protocol by using a new digital device during the staged CCFT when compared to surface electromyography (sEMG) of neck flexor muscles in participants with bruxism.

Methods

Cross-sectional pilot study including five participants with bruxism and five controls. Measuring five incremental stages (20-100%), from a maximum force of 17 N for the CCFT and parallel to sEMG measurements of bilateral sternocleidomastoideus (SCM) and masseter muscles. SEMG data were normalized to their activity during maximal voluntary contraction. Performance during the staged CCFT was fed back via a smartphone screen.

Results

A two-way repeated measures ANOVA found a significant stage (F = 32.56, df = 4, p = 0.001) but not group (0.30, df = 1, p = 0.65) main effect for SCM activity, with both groups demonstrating higher normalized sEMG activity for incremental stages of the CCFT. Neither group nor stage effects were found for normalized masseter activity during the staged CCFT.

Conclusion

A new measurement protocol and test device for the CCFT were examined in participants with and without bruxism. In parallel, sEMG used showed differences in SCM activity for incremental test stages. Group differences could not be found.