Long-term clinical and radiographic outcomes of Michigan-type stabilization splint therapy on patients with temporomandibular joint degenerative joint disease: a CBCT-based retrospective cohort study.

OBJECTIVES: To evaluate the long-term efficacy of Michigan-type stabilization splint (SS) therapy on clinical symptoms and osseous structural changes in patients with temporomandibular joint degenerative joint disease (TMJ DJD). MATERIALS AND METHODS: This retrospective cohort study analyzed 30 patients diagnosed with TMJ DJD who underwent 1-year full-time SS therapy. Clinical records and cone-beam computed tomography (CBCT) data were systematically collected at baseline (T0), 3 years post-treatment (T1), and long-term follow-up (T2 ≥ 4 years). Longitudinal changes in clinical symptoms (pain, mouth opening, clicking) and radiographic joint morphology (joint space, bone scores) were assessed. RESULTS: At the 3-year follow-up (T1), 83.3% of patients reported significant pain relief (p < 0.001), a benefit that was sustained at the long-term follow-up (T2). While maximal mouth opening and joint clicking prevalence remained statistically stable, distinct individual trajectories were observed. Radiographically, condyles showed significant spatial repositioning with expanded superior (+ 0.53 mm, p < 0.001) and posterior (+ 0.69 mm, p = 0.034) joint spaces. However, regarding osseous integrity, hyperplasia progressed significantly (p = 0.005), and total bone scores increased over time (p < 0.05), indicating ongoing degenerative changes despite symptomatic relief. CONCLUSIONS: Michigan-type SS therapy provides durable symptomatic relief and induces favorable joint space adaptations but does not arrest the progression of osseous degeneration over the long term. These findings suggest that splints primarily facilitate biomechanical adaptation and load redistribution rather than structural regeneration.