Stress Analysis of Clasps Made of Glass Fiber-reinforced Composite Material Using Three-dimensional Finite Element Method: Influence of Shape in Cross and Longitudinal Sections of Circumferential Clasp Arms

Abstract

The purpose of this study was to investigate the effects of different cross-sectional shapes and presence of taper on stress distribution in clasp arms made of glass fiber-reinforced composite (FRC) material. Stress analysis of clasps was performed under a constant load (5 N) using a three-dimensional finite element method with due consideration to the anisotropy of unidirectional FRC material. Results were then compared with clasp arms made of metal -an isotropic material. It was found that both FRC clasps and metal clasps yielded similar results. As for the displacement of clasp arms with a basic cross-sectional shape under a load of 5 N, the amount of displacement showed that FRC clasps provided sufficient retentive force required for clinical application.

Optimum design for glass fiber-reinforced composite clasps using nonlinear finite element analysis

“…The coating layer was omitted in this study to allow comparison of the nonlinear FEA results with our previous experimental measurements 14,16) .…”

“…The axis1 and 2 were mutually perpendicular in the transverse plane and perpendicular to the axis3 (the running direction of fibers). Nine elastic constants (Table 2) were used as in our previous study 14) . These were set by assuming the use of Vectris Pontic (Ivoclar Vivadent, Amherst, NY, USA), which we used for material testing and clinical trials [1][2][3][4] .…”

“…Element types used in this analysis were a hexahedral element with eight nodes for the FRC clasp arm and a tetrahedral element with four nodes for the abutment tooth. To define the orthotropy of the FRC material, local coordinate systems are necessary for defining the orientation of the fibers (the material's principal axis) 14) . Hexahedral elements can define the local coordinate systems more easily than other element types, and we used these in this study and in our previous study 14) .…”

“…FRC was treated as an elastic orthotropic material according to the local cylindrical coordinate systems 14) for defining the material's principal axis. In this coordinate system, three significant directions (axis1, axis2 and axis3 direction) were defined to input elastic constants of the orthotropic material.…”

“…There were no prior reports of anisotropic analysis based on the assumption that clasp arm shape is geometrical. Therefore, we established a linear elastic FEA procedure that took into account the anisotropy of the FRC material 14) . However, a nonlinear FEA procedure, which took into account geometric nonlinearity and nonlinear boundary conditions, appears indispensable for a more quantitative evaluation of the retentive forces and the effect of stresses.…”