Influence of Fine Threads and Platform-Switching on Crestal Bone Stress Around Implant—A Three-Dimensional Finite Element Analysis
The aims of this study were to investigate the effect of implant fine threads on crestal bone stress compared to a standard smooth implant collar and to analyze how different abutment diameters influenced the crestal bone stress level. Three-dimensional finite element imaging was used to create a cross-sectional model in SolidWorks 2007 software of an implant (5-mm platform and 10 mm in length) placed in the premolar region of the mandible. The implant model was created to resemble a commercially available fine thread implant. Abutments of different diameters (5.0 mm: standard, 4.5 mm, 4.0 mm, and 3.5 mm) were loaded with a force of 100 N at 90° vertical and 40° oblique angles. Finite element analysis was done in COSMOSWorks software, which was used to analyze the stress patterns in bone, especially in the crestal region. Upon loading, the fine thread implant model had greater stress at the crestal bone adjacent to the implant than the smooth neck implant in both vertical and oblique loading. When the abutment diameter decreased progressively from 5.0 mm to 4.5 mm to 4 mm and to 3.5 mm the thread model showed a reduction of stress at the crestal bone level from 23.2 MPa to 15.02 MPa for fine thread and from 22.7 to 13.5 MPa for smooth collar implant group after vertical loading and from 43.7 MPa to 33.1 MPa in fine thread model and from 36.9 to 20.5 MPa in smooth collar implant model after oblique loading. Fine threads increase crestal stress upon loading. Reduced abutment diameter that is platform switching resulted in less stress translated to the crestal bone in the fine thread and smooth neck.
Figure 1. Finite element mesh assembly showing cortical and cancellous bone dimension with implant. Figure 2. Cross-section assembly view showing cortical (color orange) and cancellous bone (color red) along with implant (color gray). Figure 3. Implant mesh model. Figure 4. Implant model. Figure 5. Abutment, 3 mm in length (color gray).
Figure 6. Implant lower body thread dimensions. Figure 7. Von Mises Stress Plot 3.5-mm smooth implant surface. Figure 8. Von Mises Stress Plot 3.5-mm fine thread. Figure 9. Stress plot 3.5-mm smooth implant surface with 40° oblique load. Figure 10. Stress plot 4.5-mm fine thread implant surface.
Figure 11. Stress plot 4.5-mm with 40° oblique load. Figure 12. Stress plot 5-mm smooth implant surface. Figure 13. Stress plot 5-mm smooth implant collar oblique load. Figure 14. Stress plot 5-mm fine thread oblique load. Figure 15. Stress plot 5-mm fine thread implant surface with 40° oblique load (Translucent).
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