CBCT and Audiological Analysis of the TMJ-Tinnitus Relationship

Investigation of the Interaction Between Temporomandibular Joint and Tinnitus Using CBCT and Audiological Methods: A Prospective Cross-Sectional Study

The aim of this study is to investigate the relationship between Temporomandibular Disorders (TMD) and subjective tinnitus at both morphological and functional levels. Current literature suggests that somatosensory inputs from the temporomandibular joint (TMJ) and masticatory muscles can modulate auditory pathways, a phenomenon known as Somatosensory Tinnitus. However, the specific role of TMJ bone morphology and critical neighboring structures, such as the Petrotympanic Fissure (PTF), in this interaction remains unclear.

In this clinical study, patients with tinnitus will undergo a comprehensive evaluation including Cone Beam Computed Tomography (CBCT) to quantitatively analyze condylar morphology and osteoarthritic changes. Additionally, audiological tests will be performed to assess the functional state of the auditory system. This multidisciplinary approach aims to clarify the biological link between TMD and tinnitus, potentially improving diagnostic protocols and highlighting the importance of TMJ stabilization in tinnitus management.

Background and Rationale:

Tinnitus is defined as the conscious perception of sound in the absence of an external acoustic source. Subjective tinnitus, the most common form, is often associated with neuroplastic changes in the central auditory pathways. A specific subtype, Somatosensory Tinnitus (ST), occurs when afferent somatosensory input from the upper cervical or temporomandibular region modulates tinnitus perception. This interaction is mediated through neural connections between the Dorsal Cochlear Nucleus (DCN) and somatosensory nuclei in the brainstem. Clinical observations indicate a high prevalence of Temporomandibular Disorders (TMD) among tinnitus patients, suggesting a biological link where TMD symptoms (pain, restricted movement, and muscle activity) influence the spontaneous neuronal firing rates in the auditory centers.

Study Objectives:

While evidence points to a strong interaction between TMJ somatosensory input and tinnitus, the roles of auditory function and TMJ bone morphology-specifically condylar changes and the Petrotympanic Fissure (PTF)-remain under-investigated. This study aims to provide a comprehensive multidisciplinary analysis by evaluating the auditory system through audiological tests and examining morphological changes in TMJ bone tissues using Cone Beam Computed Tomography (CBCT).

Methodology:

Patients presenting to the Otorhinolaryngology (ENT) clinic with otological complaints (tinnitus and ear pain) and suspected of having TMD will be referred to the Dentomaxillofacial Radiology clinic.

Clinical Evaluation: A standardized anamnesis will be recorded, including demographics, systemic health, and bruxism history. Physical examination will involve bilateral palpation of the TMJ and masticatory muscles, alongside measurements of maximum mouth opening, lateral excursions, and protrusive movements.

Radiographic Protocol: CBCT images will be acquired using the Instrumentarium OP300 Dental unit (89 kvP, 4-12 mA) with patients in an upright position and maximum intercuspation.

Image Analysis: Using OnDemand 3D Dental software, a radiologist with 10 years of experience will evaluate:

Condylar Morphology: Classified as convex, round, angled, or flat.

Osteoarthritic Changes: Presence of flattening, resorption, subchondral cysts, sclerosis, and osteophytes.

Glenoid Fossa & PTF: Fossa depth will be measured. The PTF morphology will be categorized according to the Sato et al. classification:

Type 1 (Open): Fissure clearly visible.

Type 2 (Partially Open): Fissure partially closed.

Type 3 (Closed): Fissure completely ossified.

Hypothesis:

The investigators hypothesize that normalizing afferent input from the temporomandibular region through multidisciplinary TMD management may alleviate tinnitus symptoms, and that specific morphological variations in the TMJ/PTF complex are correlated with the severity of subjective tinnitus.

Inclusion Criteria:

• Patients aged 18 years and older.
• Patients presenting with otological symptoms such as tinnitus and ear pain.
• Patients diagnosed with Temporomandibular Disorders (TMD) based on clinical and radiographic examination.
• Patients who have been referred for CBCT imaging as part of their routine diagnostic process for TMD.
• Willingness to provide written informed consent to participate in the study.

Exclusion Criteria:

• Presence of objective tinnitus (e.g., vascular or muscular origin).
• History of chronic otitis media or other middle ear pathologies that could cause hearing loss or tinnitus.
• Previous history of temporomandibular joint surgery or major maxillofacial trauma.
• Presence of systemic metabolic bone diseases or inflammatory rheumatic diseases (e.g., Rheumatoid Arthritis).
• History of malignancy in the head and neck region.
• Pregnancy (due to CBCT imaging contraindication).
• Neurological or psychological disorders that would prevent cooperation during clinical and audiological examinations.