The study group will be selected from patients who previously presented with various temporomandibular disorder (TMD) complaints to the "Temporomandibular Disorders Clinic" of the Department of Complete and Removable Dentures at the Faculty of Dentistry, Istanbul University. During routine examinations, TMD-DC (Diagnostic Criteria for Temporomandibular Disorders) forms are completed to aid in achieving an accurate diagnosis. Subsequently, patients suspected of having TMD of masticatory muscle origin but without a definitive diagnosis are routinely referred for ultrasonographic (USG) imaging. Patients meeting these criteria will be included in the study.

Participants will be divided into two groups. The first group will consist of patients who have already undergone USG imaging during their routine examination, have been definitively diagnosed with masticatory muscle disorders based on clinical and radiographic findings, and have initiated routine occlusal splint therapy in the clinic. The 12-week treatment process of these patients will not be altered in any way. At the final follow-up session after the 12-week routine treatment protocol, the TMD-DC form completed at baseline will be re-administered, and the two forms will be compared to evaluate changes in symptoms and pain levels. Another USG imaging will also be performed at this session.

The second group, serving as the control group, will include patients who have previously undergone USG imaging during routine examination and have received a definitive diagnosis of masticatory muscle disorders based on clinical and radiographic evaluations, but have not yet begun treatment. Patients whose turn for treatment begins during the study period will be excluded from this group. At the end of the 12-week period, the TMD-DC form will be re-administered, and a second USG imaging will be performed. This process will not interfere with the patients' position in the treatment queue, and treatment will commence as scheduled. In the second USG session, changes in the thickness and elasticity of the masseter, temporalis, trapezius, sternocleidomastoid, and splenius capitis muscles will be assessed by comparing the two imaging records.

The study is designed as a prospective observational clinical research. The study group will consist of patients who previously presented with various temporomandibular disorder (TMD) complaints to the "Temporomandibular Disorders Clinic" of the Department of Prosthodontics at the Faculty of Dentistry, Istanbul University. During routine examinations, patients are asked to complete the TMD-DC (Diagnostic Criteria for Temporomandibular Disorders) forms to facilitate accurate diagnosis. Subsequently, patients who are suspected of having TMD of masticatory muscle origin but for whom a definitive diagnosis cannot be established are routinely referred for ultrasonographic (USG) imaging. Patients who meet these criteria will be included in the study.

Participants will be divided into two groups. The first group will comprise patients who have previously undergone USG imaging for routine diagnostic purposes, have been definitively diagnosed with masticatory muscle disorders based on clinical and radiographic examinations, and have initiated occlusal splint therapy as part of routine clinical care. The 12-week treatment protocol of these patients will not be altered in any way. At the final follow-up session at the end of the 12-week treatment period, the TMD-DC form previously completed at baseline will be re-administered, and the two forms will be compared to evaluate changes in patients' symptoms and pain levels. Additionally, a second USG imaging will be performed at this session.

The second group will consist of patients who have undergone USG imaging for routine diagnostic purposes, have been definitively diagnosed with masticatory muscle disorders based on clinical and radiographic findings, but have not yet begun treatment due to waiting their turn in the treatment queue. Patients who start occlusal splint therapy during the study period will be excluded from the control group. This group will serve as the control group of the study. At the end of the 12-week observation period, participants in this group will again complete the TMD-DC form and undergo a second USG imaging. This process will not affect their place in the treatment queue, and treatment will be initiated when their turn arrives.

In the final USG session, the thickness and elasticity of the masseter, temporalis, trapezius, sternocleidomastoid, and splenius capitis muscles will be compared between the two imaging sessions. In this way, the effects of occlusal splints on the morphology and elasticity of the head and neck muscles will be evaluated.

Inclusion Criteria:

Patients who have presented to the Faculty of Dentistry at Istanbul University with temporomandibular disorder (TMD) complaints, Patients diagnosed with myospasm and/or myofascial pain syndrome in the masseter and/or temporalis muscles prior to treatment, Patients with no physical or mental disabilities, Patients over the age of 18, Patients who have not previously received any treatment for TMD.

Exclusion Criteria:

Patients with any type of TMD other than masticatory muscle disorders, Patients who have previously received any form of TMD treatment, Patients under the age of 18.

The researcher performing the ultrasonographic imaging is blinded to the group allocation of the patients. The study is designed as a single-blind trial.