Assessing the temporomandibular joint effects of non-transport disc distraction osteogenesis in a canine model: an integrated finite element and CBCT study

This study established a canine model of non-transport disc distraction osteogenesis (NTDDO) to reconstruct segmental mandibular defects and evaluated its impact on temporomandibular joint (TMJ) biomechanics. Cone Beam computed tomography (CBCT) tracked new bone regeneration in the distraction gap and condylar changes. Three-dimensional finite element analysis (FEA) models were developed to assess the stress changes of condyles, articular discs and distractor at different time points. Condyles and articular discs histological changes were observed. The results showed that the newly formed bone increased in density with prolonged consolidation. On the healthy side, the lateral pole of the condylar head translated forwards and downwards, and the condyle underwent clockwise rotation in both the orbital-auricular and coronal planes. On the distracted side, the medial pole of the condylar head moved downwards, with the condyle rotating clockwise in the coronal plane postoperatively. However, comparisons of the overall condylar positions preoperatively, at the end of distraction, and after eight weeks of consolidation revealed no statistically significant changes. At the postoperative period, FEA revealed a concentrated area of stress on both condyles and articular discs, whereas the stress distribution was relatively uniform preoperatively and after 8 weeks of consolidation. The maximum stress of the distractor occurred at the joint between the distractor wing and the bar. Histological analysis of the condyles and articular discs harvested from stress concentration zones showed intact cartilage structure. The established NTDDO model effectively repairs segmental mandibular defects while inducing temporary TMJ biomechanical alterations without causing irreversible joint damage.