Accuracy of Digital Mandibular Repositioning in Occlusal Reconstruction for Patients With Disc Displacement

Detailed Description This study evaluates four different methods for mandibular repositioning in patients with bilateral reducible temporomandibular joint (TMJ) disc displacement requiring occlusal reconstruction.

Methods of Mandibular Repositioning:

• Intraoral Direct Positioning Group: The therapeutic jaw position is determined clinically using the clicking elimination method, where patients open wide until clicking occurs, then gradually retract the mandible while performing opening-closing movements to find the minimal protrusion position without clicking.
• Articulator Positioning Group: Uses mechanical facebow transfer and semi-adjustable articulator (Artex CR) with condylar guidance parameters obtained from protrusive and lateral excursion records. The therapeutic position is determined by analyzing CBCT joint space measurements and MRI disc displacement data.
• Digital Anatomical Positioning Group: Combines intraoral scanning data with CBCT-reconstructed 3D jaw models. The therapeutic position is determined by referencing MRI disc reduction phase, optimal joint space ratios, and anatomical landmarks using CAD software (Exocad).
• Digital Jaw Motion Tracking Group: Integrates 3D jaw models with electronic jaw tracking data (Zebris). The therapeutic position is determined by analyzing condylar movement trajectories (identifying the "figure-8" pattern crossover points indicating disc displacement) combined with dynamic MRI and optimal joint space parameters.

Treatment Protocol: All groups receive digitally designed and manufactured repositioning splints. Patients wear splints 24 hours daily (except during meals) for 3 months, with follow-up adjustments at 2 weeks, 1 month, 2 months, and 3 months.

Imaging Protocol:

• CBCT (I-CAT FLX): 120 kV, 5 mA, 0.2 mm resolution
• MRI (GE Discovery MR750w 3.0T): Bilateral TMJ surface coils, oblique sagittal and coronal views in closed-mouth position, oblique sagittal in maximum opening

Assessment Methods:

• Joint space measurements using Ikeda's method on registered pre- and post-treatment CBCT images
• Condyle position analysis using Gelb 4/7 position criteria
• Disc-condyle angle measurement on MRI (>15° defined as disc displacement)

Inclusion criteria

• Diagnosis of reducible temporomandibular joint (TMJ) disc displacement according to the 2014 revised criteria of the International Association for Dental Research;
• Bilateral reducible disc displacement confirmed by MRI;
• Reproducible joint clicking during mandibular opening and closing;
• Permanent dentition with full cognitive and communicative ability;
• Signed informed consent with good treatment compliance.

Exclusion criteria

• Non-reducible disc displacement, osteoarthrosis, isolated myofascial pain, or other conditions not meeting diagnostic criteria;
• Receipt of other TMJ disorder treatments within the past 3 months;
• Presence of systemic diseases, psychiatric disorders, or impaired consciousness.