An exploration of the correlation between strain energy density in the temporomandibular joint and facial morphologic parameters

Purpose: The purpose of this was to construct finite element (FE) models based on computed tomography (CT) data of individual patients during orthodontic treatment and to evaluate the relationship between strain energy density (SED) in the temporomandibular joint (TMJ) disc and the facial morphology of three skeletal patterns (Class 1–3) by cephalometric analysis. Methods: Cephalometric analyses were performed on 53 patients. FE models based on the CT images of each patient were constructed, and the mean SED in the bilateral TMJ disc was calculated. The relationships between SED and the cephalometric parameters were evaluated. Results: SED was significantly greater in Classes 1 and 2 than in Class 3 ( p < 0.05). A positive correlation was observed between SED and the parameter of, convexity and ANB angle ( p < 0.01), whereas a negative correlation was observed between SED and facial angle in Class 3( p < 0.05). A positive correlation was identified between SED and gonial angle in Class 1( p < 0.05). In all cases, correlations were observed between SED and facial angle ( p < 0.05), convexity( p < 0.01), mandibular angle( p < 0.05), Y-axis( p < 0.05), SNB ( p < 0.05), ANB angle( p < 0.01), and overjet( p < 0.05). Conclusion: An increase in SED in the TMJ disc was observed when the mandible was rotated clockwise and positioned superior posteriorly. Furthermore, SED was affected by an overjet of dental parameters. Numerically, the present study suggests that SED generated in the TMJ disc was primarily affected by mandibular morphology. Considering that an increase in SED causes damage to the articular disc, three skeletal parameters (facial angle, convexity, and ANB) are useful in predicting TMJ dysfunction.