CBCT and Audiological Analysis of the TMJ-Tinnitus Relationship

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.

• Cone Beam Computed Tomography (CBCT) (Diagnostic test): High-resolution 3D imaging of the temporomandibular joint (TMJ) using the Instrumentarium OP300 Dental unit. The procedure involves evaluating condylar morphology, osteoarthritic changes (flattening, resorption, osteophytes), and the anatomical structure of the Petrotympanic Fissure (PTF) based on the Sato et al. classification.
• Audiological Assessment (Diagnostic test): A comprehensive evaluation of the auditory system to determine hearing thresholds and the functional status of the ear. This includes pure tone audiometry and specific tests to characterize the frequency and intensity of tinnitus in the patient group.
• Clinical TMJ Examination (Other): Systematic physical examination of the masticatory muscles and the TMJ. This includes bilateral palpation for pain and tenderness, assessment of mandibular range of motion (maximal mouth opening, lateral and protrusive movements), and recording of joint sounds (clicking or crepitation).

Primary outcomes

• Frequency of Petrotympanic Fissure (PTF) Morphological Types [Baseline (at the time of the single CBCT scan during the initial clinical visit).]: The morphology of the PTF will be categorized into three types according to the Sato et al. classification: Type 1 (Open), Type 2 (Partially Open), and Type 3 (Closed) using CBCT imaging.

Secondary outcomes

• Presence of Osteoarthritic Changes in the Mandibular Condyle [Baseline.]: Evaluation of degenerative changes including flattening, resorption, subchondral cysts, generalized sclerosis, and osteophytes on CBCT images. Each change will be recorded as "present" or "absent".
• Pure Tone Thresholds [Baseline]: Evaluation of hearing levels across standard frequencies (250 Hz to 8000 Hz) measured in decibels (dB).
• Maximum Pain-Free Mouth Opening [Baseline.]: Measurement of the distance between the incisal edges of the upper and lower central incisors during maximum mouth opening, recorded in millimeters (mm).

Sex: All, ages: 18 Years to any

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.

• Results publication: Cakur B, Yasa Y. Correlation Between Tinnitus and Petrotympanic Fissure Status Among Patients With Temporomandibular Joint Dysfunction. J Oral Maxillofac Surg. 2016 Jan;74(1):47-52. doi: 10.1016/j.joms.2015.07.020. Epub 2015 Jul 31. PMID 26279489
• Results publication: Buergers R, Kleinjung T, Behr M, Vielsmeier V. Is there a link between tinnitus and temporomandibular disorders? J Prosthet Dent. 2014 Mar;111(3):222-7. doi: 10.1016/j.prosdent.2013.10.001. Epub 2013 Nov 25. PMID 24286640
• Results publication: Sato I, Arai H, Asaumi R, Imura K, Kawai T, Yosue T. Classifications of tunnel-like structure of human petrotympanic fissure by cone beam CT. Surg Radiol Anat. 2008 Jun;30(4):323-6. doi: 10.1007/s00276-008-0327-4. Epub 2008 Feb 21. PMID 18288438