الفهرس 
Comparative study between two types of bar attachments (bar joint and bar unit) in implant supported overdenture element : 3-d finite element stress analysis
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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.