Temporomandibular Disorders With and Without Chronic Neck Pain

Temporomandibular disorders (TMD) are among the most prevalent musculoskeletal conditions affecting the temporomandibular joint, masticatory muscles, and associated structures. These disorders are characterized by pain, restricted mandibular movement, joint sounds, and impaired jaw function, resulting in limitations in daily activities and reduced quality of life. Increasing evidence suggests that TMD should not be considered an isolated disorder of the temporomandibular joint but rather a complex musculoskeletal condition involving close anatomical, biomechanical, and neurophysiological interactions with the cervical spine. The trigeminocervical complex provides a neurophysiological basis for this relationship by integrating afferent input from both the cervical spine and the trigeminal system, thereby influencing pain processing, motor control, and sensorimotor function.

Individuals with TMD frequently demonstrate forward head posture, reduced cervical range of motion, impaired deep cervical flexor muscle function, and altered cervical proprioception. Although previous studies have reported associations between cervical dysfunction and temporomandibular symptoms, most investigations have evaluated only isolated components of cervical function. Furthermore, the specific influence of chronic neck pain on cervical impairments and its contribution to temporomandibular function has not been comprehensively investigated. Therefore, a more integrated evaluation of cervical posture, mobility, muscle endurance, and proprioception is warranted to better understand the interaction between cervical dysfunction and TMD.

The primary objective of this cross-sectional study is to compare cervical function and temporomandibular characteristics between individuals with TMD accompanied by chronic neck pain and those with TMD without chronic neck pain. A secondary objective is to determine which cervical variables independently predict temporomandibular function, maximal mouth opening, and temporomandibular pain intensity.

A total of 67 adults diagnosed with TMD according to the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) will participate in the study. Participants will be recruited from the Tunceli Oral and Dental Health Center and divided into two groups according to the presence or absence of chronic neck pain. Individuals in the chronic neck pain group must have experienced neck pain for at least three months, report neck pain on the Visual Analog Scale (VAS), and have a Neck Disability Index (NDI) score of at least 5. Participants without chronic neck pain must report no neck pain during the previous three months, have a VAS score of zero, and an NDI score below 5. Eligible participants will be between 18 and 65 years of age and diagnosed with TMD according to the DC/TMD criteria. Individuals with cardiac, pulmonary, neurological, orthopedic, or other systemic diseases, infection, malignancy, previous cervical spine surgery, acute cervical trauma or fracture, or cognitive or psychological conditions that could interfere with the assessments will be excluded.

All participants will undergo standardized clinical assessments performed by trained investigators. Temporomandibular joint function will be evaluated by measuring maximal mouth opening, lateral excursion, and protrusion range of motion. Functional limitation related to TMD will be assessed using the Jaw Functional Limitation Scale-20 (JFLS-20). Cervical posture will be evaluated by measuring the craniovertebral angle using the PostureScreen application. Total cervical range of motion will be measured with a Cervical Range of Motion (CROM) device. Deep cervical flexor muscle endurance will be assessed using the Craniocervical Flexion Test. Cervical proprioception will be evaluated using the Joint Position Error Test. Neck disability will be assessed using the Neck Disability Index (NDI), while temporomandibular joint pain intensity and neck pain intensity will be measured using the Visual Analog Scale (VAS).

Statistical analyses will include comparisons between groups using independent-samples t-tests. Associations between cervical and temporomandibular variables will be examined using Pearson correlation analyses. Multiple linear regression and hierarchical regression analyses will be performed to identify independent cervical predictors of temporomandibular function, maximal mouth opening, and temporomandibular pain intensity. Statistical significance will be defined as a two-sided p-value of less than 0.05.

This study is expected to improve the understanding of the relationship between cervical dysfunction and temporomandibular disorders by comprehensively evaluating multiple components of cervical function within the same population. The findings may provide clinically relevant evidence supporting comprehensive cervical assessment and the integration of cervical-focused rehabilitation strategies into the management of individuals with temporomandibular disorders.