Objectives: The biomechanical behavior of the superstructure plays an important role
in the functional longevity of dental implants. However, information about the influence
of framework design on stresses transmitted to the implants and supporting tissues
is limited. The purpose of this study was to evaluate the effects of framework designs
on stress distribution at the supporting bone and supporting implants.
Methods: In this study, the three-dimensional (3D) finite element stress analysis
method was used. Three types of 3D mathematical models simulating three different
framework designs for implant- supported 3-unit posterior fixed partial dentures were
prepared with supporting structures. Convex (1), concave (2), and conventional (3)
pontic framework designs were simulated. A 300-N static vertical occlusal load was
applied on the node at the center of occlusal surface of the pontic to calculate the
stress distributions. As a second condition, frameworks were directly loaded to evaluate
the effect of the framework design clearly. The Solidworks/Cosmosworks structural
analysis programs were used for finite element modeling/analysis.
Results: The analysis of the von Mises stress values revealed that maximum stress
concentrations were located at the loading areas for all models. The pontic side marginal
edges of restorations and the necks of implants were other stress concentration regions.
There was no clear difference among models when the restorations were loaded at occlusal
surfaces. When the veneering porcelain was removed, and load was applied directly
to the framework, there was a clear increase in stress concentration with a concave
design on supporting implants and bone structure.
Conclusions: The present study showed that the use of a concave design in the pontic
frameworks of fixed partial dentures increases the von Mises stress levels on implant
abutments and supporting bone structure. However, the veneering porcelain element
reduces the effect of the framework and compensates for design weaknesses. (Eur J
Dent 2010;4:374-382)
Keywords
Framework design - Implant supported fixed partial denture - 3-D FEM - Pontic design
