Associations between condylar height relative to occlusal plane and condylar osseous condition and TMJ loading based on 3D measurements and finite element analysis

To investigate the relationship between condylar height relative to occlusal plane (CHO) and condylar osseous condition and the changes of condylar stress loading before and after CHO modifications. The condylar osseous conditions of 434 temporomandibular joints (TMJ) were assessed and grouped. Measurements of anatomical parameters were performed on CT-based reconstructed 3D stomatognathic models. Differences in anatomical parameters of the jaws in the different groups were compared, and the correlation between the Angle α (representing the CHO ratio) and related parameters was investigated. A finite element model (FEM) was constructed using 3D finite element analysis (FEA). The Angle α was altered by modifying condylar position and the inclination of mandibular plane (MP) and occlusal plane (OP) based on the FEM to analyze condylar stress loading under different working conditions. There were differences in anatomical parameters among the different groups, with the smaller Angle α in the osseous destruction group. Angle α was negatively correlated with the inclination of MP and OP. The FEA illustrated condylar stress loading changed after modifying the Angle α by both two modalities. After modifying condylar position, the stress increased with the proximal movement of the condyle toward the OP. After changing the inclination of MP and OP, the stress increased with increasing inclinations. Changes in CHO correlate with condylar osseous condition, and distal movement of the condyle to the OP and reduction of MP and OP inclination may reduce TMJ stress overload. In clinical practice, it is advisable to assess patients for sufficient CHO ratio, as insufficiency in CHO may elevate the risk of TMJ stress overload. The CHO ratio could be modulated by changing the inclination of the OP.