Correlation between 3-dimensional facial morphology and mandibular movement during maximum mouth opening and closing

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The purpose of this study was to analyze the relationship between mandibular movement and facial morphology parameters measured using 3-dimensional CT data. We have developed a mandibular movement tracking and simulation system. The mandibular movement data were acquired from 22 subjects (6 males and 16 females), 3 who had no clinical facial deformities and 19 who had orthofacial deformities. The subjects voluntarily performed maximum mouth opening and closing movements. Three-dimensional maximum linear movements of selected points (bilateral condylions, infradentale, and pogonion) were calculated to represent mandibular movement. Facial morphology values were measured 3-dimensionally from CT data and bilateral morphological values were divided into 2 groups according to the mandibular deviation, the deviated side, and counter-deviated side groups. Correlation coefficients were calculated to evaluate the relationship between mandibular movements and facial morphology. Maximum linear movements of all selected points on the mandible were positively correlated with sella-nasion-point A (SNA) and sella-nasion-point B (SNB). Movements of the infradentale and pogonion were significantly correlated with ramus inclination, lateral mandibular body angle, ramus length, and mandibular body length. Condylar movement was positively correlated with lateral mandibular body angle and mandibular body length. Multiple stepwise linear regression analysis was performed to evaluate the model predicting the effect of morphological values on mandibular movement. Condylar movement was associated with the SNA (R(2) value = 0.32 for the deviated side, R(2) value = 0.26 for the counter-deviated side), and movement of the infradentale was associated with both SNA and ramus length (R(2) value = 0.57). Movement of the pogonion could be predicted by SNA, mandibular length, and condylar head length (R(2) value = 0.65). The 3D facial morphology values were associated with variations in mandibular movement, and morphological parameters contributed to predicting the movement of the mandible with different degrees.