الفهرس | Only 14 pages are availabe for public view |
Abstract The current finite element study compared the stress patterns induced by bar attachment with different marital (bar unit and bar joint) when used to retain mandibular overdentures ported by two root form dental implants. The outline and geometry of an edentulous mandible were detected using images by a digital camera. The geometrical models were then created simulating the implant abutment complex, supporting cortical bone, cancellous bone and mucosa as well as the overdenture and bar/clip. After construction of the components of the study, they were exported to the ANSYS 9 program, and assembled together to obtain a finite element model, containing all the structures of the study. All materials were assumed to be isotropic, homogenous and linearly elastic The three-dimensional models simulated a clinical situation where an edentulous mandible was restored by two different treatment options using implant overdentures. The overdentures were supported by two implants placed at the approximate canine region using bar attachment. The load was applied of value of 50,100,150 N with angle of vertical 90° then the oblique load with angel 45°and load applied by 100 from the lingual direction on the left premolar/molar region. The generated stresses were calculated numerically in Mega Pascal and were plotted graphically for better evaluation The results of this study showed that the stresses generated by the application of vertical or oblique loads varied according to the type of attachment Connected to the implant used to support the overdenture. 7.2 Conclusions: Within the limitations of this study, the following conclusions can be drawn: Overdenture: The overdenture is fairly affected by the bar design, that sharp edged bar slightly increases stresses on overdenture in comparison to round one. Mucosa: Mucosa is relaxed by using the round bar that is it reduces the overdenture pressing on mucosa tissue. Although the mucosa stresses and deformations were within the physiological limits, sharp edged bars may cause more pain if compared with round one. Clips: The caps on round bars were subjected to high level of stresses that do not ensure long life time. Generally, sharp edged bars are preferred for longer maintenance period. Bar: Both bar designs withstand the applied load perfectly while sharp edged one was slightly better than round one for its less deformation and stresses. Implants: The used type and size of implants are safe for use under all simulated loading conditions. It showed typical maximum stress location at its neck. Implant abutment complex was not sensitive to bar design. Bone: Although using bar is not recommended for patients with flat ridge, the bone was not sensitive to bar design. |