Assessment of orofacial motor functions in TMD patients over the course of treatment with a modified occlusal splint

Background. Temporomandibular disorders (TMD) significantly affect patients’ quality of life due to impaired orofacial motor functions, including chewing, swallowing, speech, and facial expressions. The assessment of treatment dynamics should rely on quantitative, objective data, such as surface electromyography (EMG), which allows the evaluation of muscle activity and coordination during various functional tasks. Objective: to study orofacial motor functions in patients with TMD through the quantitative analysis of interference EMG signals in the masticatory and temporal muscles, to calculate relevant indices, and to describe changes in muscle activity during chewing before and after treatment with a modified occlusal splint. Materials and methods. From 325 examined individuals, 85 patients (63 females (74 %) and 22 males (26 %), mean age 36.2 ± 10.8 years) with TMD were selected for analysis by randomization. All patients were divided into three groups based on the DC/TMD classification. Symptoms of physical pain and TMD were evalua­ted through questionnaires. The functional state of the muscles was assessed using electromyography. Statistical evaluation of the results was conducted with ANOVA and non-parametric Kruskal-Wallis and Wilcoxon tests. Results. Before treatment, orofacial motor control in TMD patients was impaired: in group II (myalgias), the Functional Activity Index (FI ATTIV) was –13.9 ± 4.8 %; in group III (combined pathologies), –6.8 ± 3.5 %, whereas in group I (disk disorders), partial preservation of masticatory muscle activity was observed (8.3 ± 5.9 %). Muscle overload on the balancing side was observed before treatment: As dextra in group I was 139.0 ± 30.7 %, in group II, 102.7 ± 15.9 %, in group III, 127.6 ± 22.9 %; As sinistra in group I was 122.8 ± 19.7 %, in group II, 124.3 ± 20.9 %, in group III, 130.5 ± 19.6 %. Post-treatment, FI ATTIV showed signifi­cant improvements: in group I, 7.0 ± 3.1 % (p > 0.05), in group II, 6.3 ± 2.4 % (p = 0.027), and in group III, 5.7 ± 3.4 % (p = 0.046). The asymmetry index (As, %) also demonstrated notable improvements: As dextra in group II reached 152.4 ± 31.2 % (p = 0.019) and in group III, 173.5 ± 37.4 % (p = 0.021); As sinistra in group II was 156.5 ± 33.8 % (p = 0.026) and in group III, 154.8 ± 21.5 % (p = 0.014). Conclusions. Quantitative EMG analysis showed that treatment with a modified occlusal splint effectively improves muscle balance, restores coordination between the working and balancing sides, and reduces pain in TMD patients.