Temporomandibular joint disc position affects condylar bone modeling – a randomized controlled clinical trial

Backgrounds: The primary controversy surrounding the treatment of anterior disc displacement (ADD) of temporomandibular joints (TMJ) stems from the unclear relationship between disc position and condylar adaptation. The long-term impact of varying disc position on condylar bone remodeling remains poorly understood. Methods: A randomized controlled clinical trial was conducted to evaluate the effects of different disc positions on condylar bone modeling/remodeling at baseline (T0) and after an 18-month follow-up (T1). Patients under 25 years of age diagnosed with TMJ ADD without reduction (ADDwoR) were enrolled and randomly allocated in a 1:1 ratio to either the disc displaced (DD) group or the disc reposited (DR) group. Participants in the DR group underwent arthroscopic disc repositioning surgery, whereas those in the DD group received no occlusal or surgical intervention. CT scans were obtained at T0 and T1, and three-dimensional condylar reconstructions were generated using Mimics 21.0 software. Seven anatomical points were defined on the condylar surface to represent distinct regions. The condylar volume and vertical height of 7 points were measured for the analysis. Results: This study included 60 patients with ADDwoR. At T1, the DR group demonstrated a significant increase in total condylar volume of 279.6 mm 3 per patient, compared to a slight 29.5 mm 3 increase in the DD group ( P < 0.0001). Differential height changes were observed between groups, particularly at the posterolateral and lateral condylar surfaces ( P < 0.05). Besides, anterolaterally displaced discs were associated with bone resorption at the posteromedial condyle, in contrast to anteromedially displaced discs at T0 ( P < 0.01). Conclusions: This study provides compelling evidence that ADDwoR restricts condylar bone growth in adolescents and young adults. Furthermore, disc position directly determines patterns of condylar bone modeling and remodeling in this population.