Human jaw joint hypermobility: Diagnosis and biomechanical modelling

Area of Science:

• Biomechanical Engineering
• Craniofacial Anatomy
• Temporomandibular Joint Disorders

Background:

• Hypermobility disorders of the jaw joint cause symptoms like clicking and instability, potentially leading to subluxation or luxation.
• Differentiating hypermobility from disc displacements is crucial for accurate diagnosis and treatment.
• Previous biomechanical models suggested the anterior slope angle of the eminence and jaw closer orientation contribute to hypermobility.

Purpose of the Study:

• To investigate the association between clinical diagnosis of jaw joint hypermobility and predictions from patient-specific biomechanical models.
• To assess the accuracy of biomechanical models in predicting hypermobility disorders using cone-beam computed tomography (CBCT) data.

Main Methods:

• Constructed patient-specific biomechanical models of the masticatory system using CBCT data.
• Performed forward simulations of jaw opening and closing to predict hypermobility or normal function.
• Clinically diagnosed 15 patients and 11 controls using the Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) and additional tests.

Main Results:

• No significant association was found between the clinical diagnosis of hypermobility and the biomechanical model's predictions.
• Biomechanical models overestimated hypermobility cases, resulting in low specificity.
• A steeper anterior slope angle of the articular eminence was observed in patients compared to controls.

Conclusions:

• Current patient-specific biomechanical models lack the accuracy to reliably predict jaw joint hypermobility based on clinical diagnosis.
• More detailed modeling of collagenous structures (articular disc, ligaments) and the temporalis muscle is recommended.
• The steeper anterior slope angle of the articular eminence is a potential osseous factor associated with hypermobility disorders.