ABSTRACT
Objective: To explore an efficient method for the establishment of 3D finite element model based on CBCT images. Methods: Mandible of a male volunteer was scanned by CBCT, and the resulting DICOM data was used for 3D reconstruction in Mimics17 software. Then with the. stl format file, the result of 3D reconstruction was imported into Geomagic Warp 2015, in which 3D models consisting of triangular patches for dentition, periodontal ligament and alveolar bone were created. With free meshing algorithm, the 3D finite element model of mandible with full dentition consisting of 10-node tetrahedron elements was obtained under the constraint that the maximum inner angle was set to be 25°. Results: The 3D finite element model for human mandible with full dentition was established. The total number of nodes is 299286, the elements number for dentition, periodontal ligament and alveolar bone are105805, 122427 and 577529, respectively. Conclusion: The proposed method can be used for the establishment of 3D finite element model of mandible with full dentition based on CBCT images, and it has the merits of good stability, high precision and wide application compared with the traditional modeling method.
ABSTRACT
Objective@#To study the influence of two-wall bone defect on periodontal ligament stresses under normal occlusal forces, and to analyze the influence of depth and width of bone defect to periodontal ligament stresses.@*Methods@#Three-dimensional finite element models of teeth, periodontal ligament and alveolar bone were created based on cone beam CT images. Proximal two-wall bone defect with different depths (bone defect occupies one third, two thirds, and full length of root) and widths (bone defect occupies one fourth, two fourths, three fourths and full width of buccal lingual width) were simulated by modifying the elastic modulus of elements within defect areas. Occlusal forces with magnitudes of half of the maximum occlusal forces were applied to the model at an angle of 45° to the long axis of tooth, and equivalent stresses of periodontal ligament were analyzed.@*Results@#In the model of no bone defect, the equivalent stresses of periodontal ligament of incisors, canines, premolars and molars were 2.88, 2.31, 8.67 and 7.53 MPa respectively. The equivalent stresses of periodontal ligament increased with the enlargement of depth and width of bone defect. The equivalent stresses of periodontal ligament with maximum bone defect in both depth and width for incisors, canines, premolars and molars were 4.47, 3.62, 11.66 and 8.72 MPa respectively. In the model of width of bone defect was consistent and bone defect develops vertically, the increments of equivalent stresses of periodontal ligament were significantly greater in the early stage bone defect model (from no defect to one third of root length bone defect) than that in the later stage bone defect model (from two thirds to full length of root length bone defect). In the model of bone defect depth was consistent and bone defect develops transversely, the increments of equivalent stresses of periodontal ligament in the early stage bone defect model (from no defect to one fourth of buccal lingual width bone defect) were significantly smaller than that in the later stage bone defect model (from three fourths to full width of buccal lingual width bone defect).@*Conclusions@#Bone defect with shallow depth and that with large width would increase periodontal ligament stresses. Therefore, more attention should be paid to occlusion evaluation and adjustment for teeth with shallow and wide two-wall bone defect.