Cervical Proprioception, Masticatory Pain Threshold and Craniovertebral Angle in TMD

Overview

Temporomandibular disorder (TMD) is a group of conditions involving the masticatory muscles, temporomandibular joint (TMJ), and associated structures of the head, neck, and cervical region. TMD may cause pain in the ear region and over the masseter muscle, restricted mandibular movement, and clicking or crepitus sounds in the temporomandibular joint. It may also be accompanied by cervical dysfunction, limited range of motion, pain, and postural abnormalities. Due to the close anatomical and functional relationship between the cervical region and the TMJ, disorders affecting one region are likely to influence the other. Alterations in the TMJ may lead to changes in the cervical spine and consequently affect proprioception. Head posture can be evaluated using the craniovertebral angle. Increases or decreases in this angle may reflect changes in anterior head tilt. Cervical impairments associated with TMD may also result in alterations in the craniovertebral angle. Therefore, the aim of this study is to compare cervical joint position sense, pressure pain threshold of the masticatory muscles, and craniovertebral angle values between individuals with TMD and healthy controls.

Temporomandibular disorder (TMD) is a condition affecting the temporomandibular joint (TMJ), masticatory muscles, and associated structures. Patients with TMD may present with a variety of symptoms, including pain, headache, joint locking, limited mouth opening, and joint sounds. Because the cervical vertebrae are anatomically and functionally connected to the cranium and masticatory structures through neurovascular components, muscles, and joints, alterations in one region may influence the other. Shortening of the cervical extensor muscles and the sternocleidomastoid muscle may contribute to the development of a forward head posture, which is associated with increased cervical lordosis. The primary clinical manifestation of TMD is pain related to mandibular movement limitation and joint sounds during function. In addition, TMD-related pain has been reported to be associated with increased psychological distress, autonomic dysfunction, motor impairments, balance deficits, and sleep disturbances. The craniovertebral angle is defined as the angle formed between a horizontal line and a line connecting the tragus of the ear to the spinous process of the seventh cervical vertebra . It is widely used to assess head posture. In a study evaluating cranio-cervical posture using lateral radiographs, Joy et al. reported that individuals with TMD had significantly greater craniovertebral angles than healthy individuals. Proprioception is the ability to perceive joint position and movement without visual input and plays an essential role in maintaining postural balance. Proprioceptors are particularly abundant in the cervical region. Damage or dysfunction affecting the cervical spine may disrupt proprioceptive input, leading to altered head and body position, impaired postural reflexes, and deficits in balance and gait. Based on the current literature, no previous study has simultaneously compared cervical joint position sense, craniovertebral angle, and the pressure pain threshold of the masticatory muscles between individuals with TMD and healthy controls. Therefore, this study was designed to investigate these parameters comprehensively and to contribute to the existing literature.