Abstract: Objective: To explore the related factors affecting the labial inclination of maxillary central incisor, by analyzing the changes of maxillary central incisor movement during opening of anterior teeth bite with Bite Turbos under different conditions. Methods: Softwares such as Minics, Geomagic Wrap 2017, and SolidWorks were utilized for model fabrication. Workbench was employed to set the operating conditions for the models and calculate the displacement distance and direction of the maxillary central incisors. Results: In each group of models with the posterior 1/3 of the Bite Turbos occlusal surface, the upper central incisors all showed lingual displacement of the crown and labial displacement of the root. In each group with the anterior 1/3 of the Bite Turbos occlusal surface, the upper central incisors all presented labial displacement of the crown and lingual displacement of the root. Compared to the group with the standard labial inclination of the upper central incisors, in the labial inclination group, models D1, E1, and F1 exhibited more lingual inclination changes in the upper central incisors (The crown root displacement difference was more than 0.064 to 0.134 mm in the sagittal plane), while the remaining six groups displayed more labial inclination changes (0.0403-0.238) mm. In the lingual inclination group, G3, H3, and I3 demonstrated fewer labial inclination changes (0.098-0.193) mm, and the majority of the remaining six groups showed more lingual inclination (0.028-0.134) mm. When the Bite Turbos occlusal surface was inclined labially, compared to the horizontal group, all models presented more lingual inclination of the upper central incisors (0.001-0.068) mm. While when the occlusal surface was inclined lingually, all models demonstrated more labial inclination (0.009-0.171) mm. In the vertical direction, the central incisors of all groups in the models exhibited overall depression. Except for a small elongation (0.002 mm) of the incisal edge of the central incisor in group H1, the incisal edges and apical tips of the remaining groups all demonstrated depressed manifestations. Conclusion: When Bite Turbos are employed to open the bite, the variations in the labial inclination of the maxillary central incisors are closely associated with their own labial inclination, the inclination of the Bite Turbos occlusal surface, and the occlusal contact points. The relationship between the force line of the bite force and the position of the center of resistance influences the labial inclination changes of the maxillary central incisors.

Key words: three dimensional-finite element, bite turbos, biomechanical mechanism, deep overbite, maxillary central incisor lip inclination