Two Fixture Designs of Immediately Loaded Dental Implants
Immediately loaded dental implants have become very popular for implant treatment. However, most studies on immediately loaded dental implants still depended on the physician’s clinical experience and skills rather than on scientific data. Currently, there is no consensus on which implant design is best. The focus of this research is on the solid mechanics of dental implants. In this finite element analysis, two dental implant fixture designs are compared to try to determine which is best. The comparison criteria is based on the bone stress around the implant and the sliding distance between the implant and the bone.
Materials and Numerical Methods
In this study, two different geometric fixture design models are considered. One is the uniform thread model; the other is the step thread model. In the dental implant simulation, the material property is homogeneous and isotropic, the cortical bone’s Young’s modulus is 12600M Pa and the spongy bone’s Young’s modulus is 1148M Pa. The dental implant’s Young’s modulus is 70G Pa. The Poisson’s ratio of the entire simulation model is 0.3.
The 3-D finite element model is solved using the commercial software ANSYS to perform non-linear transient analysis. The tetrahedral structured meshes are generated from the geometric models of the uniform thread implant and the step thread implant. There are 197,000 tetrahedral elements and 220,000 nodes in total (Fig. 10). The surface-to-surface contact element is used to perform the loading transfers between the bone and the dental implant. There are 37,658 contact elements in the model. The bottom end of the bone in the model is fixed for all DOF and the 45 degree force, 750 N, is applied and treated as the boundary condition.
ˇ¶ Fig. 10. The simulation models
Results and Discussion
This research simulates the implantation of dental implants and examines two dental implant fixture designs: the uniform thread model and step thread model.
Fig. 11 shows the sliding distance of the step thread and uniform thread dental implants. The sliding distance between the implant and the bone is higher in the region of the upper thread and the end thread. The Maximum sliding distance is larger in the step thread implant than in the uniform thread implant. The Von Mises stress around bone is also larger in the step thread model than in the uniform thread model (Fig. 12). This implies that the step thread implant is more likely to become loose after being implanted and, therefore, the uniform thread model is superior in design.
ˇ¶ Fig. 11. The sliding distance between the two dental implants designs
ˇ¶ Fig. 12. The Von Mises stress around bone of the two dental implant designs
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