RESUMO
Objective To analyze changes of stress and displacement distribution of the mandibular condyle under different occlusal reconstruction conditions by using the Forsus, and to provide clinical reference for the application of the Forsus. Method The software Abaqus6.5 was employed to build the 3D finite element model of mandibular condyle for simulation. Under different occlusal reconstruction conditions, the distances of mandibular protraction were 3 mm, 4 mm, 5 mm, 6 mm and 7 mm and the mandibular's opening distances were got as 4 mm, 3.5 mm, 3 mm, 2.5 mm and 2 mm correspondingly. The stress, displacement and rotation trends of mandibula temporomandibular articulation were analyzed and the estimation of occlusal reconstruction contributing to the growth of the condyle was made. Results The 3D model showed that the maximum stress distributed on the mandibular condyloid process, sigmoid incisure of mandible and the posterior neck of condyle area under the five different conditions. With the increase of displacement in mandibular condyle, the stress increased slowly on the sigmoid incisure of mandible and the posterior neck of condyle area, but the stress still kept in the same order of magnitude (30 MPa). The stress distribution of mandibular condyloid process was in a steady state with no obvious stress concentration. The displacement of condyle in horizontal direction increased gradually and forward, and the displacement of condyle in vertical direction also increased gradually but downward. When the mandibular was stretched to the designed reconstructive location, the condyle moved downward. Conclusions The range of physiological occlusal reconstruction will not change the stress distribution trends of the condylar cartilage, even when the mandibular moves forwards in varying degrees. Considering the physiological nature of temporomandibular articulation and the growth of the condyle, when the mandibular retrusion is severe, it would be advisable by subsection protrusion.
RESUMO
Objective:To simulate the instantaneous distal moving trend of the maxillary first molar based on the three-dimensional finite element mode(l3-FEM)of Forsus distalizing the maxillary first molar with some visco-elastic-plastic characters and explore the favorable loading mode of molar distal movement in Forsus in order to provide biomechanical basis for clinical practice.Methods:A male patient with ClassⅡmalocclusion was selected.The 3-FEM of Forsus distalizing the maxillary first molar was built through spiral CT scanning,Mimics8.0,and Abaqus6.5 software.This study simulated instantaneous distal moving process of the maxillary first molar under three dif-ferent loading modes(loading force was 300 g,point of force was on the center of the crown's buccal surface,loading time was 1s),which included a distalizing force,a distalizing force+counterrotation moment,a distalizing force+countertipping moment+counterrotation moment.Results:When Forsus distalized the maxillary first molar,different loading modes lead to different PDL stress distributions.When the model was added by a distalizing force,the maxillary first molar would be relatively seriously inclined;when added by a distalizing force +counterrotation moment(Mt/F=9),the maxillary first molar would be relatively seriously rotated and when added by a distalizing force+ countertipping momen(tMt/F=9)+counterrotation momen(tMr/F=5),the distal surface of the PDL would bear the lightest stress,and the first molar would achieve approximate translation movement.Conclusion:When mandible is guided forward by Forsus,the maxillary first molar would achieve better molar translation effect if added certain countertipping and counterrotation moment