dr. ehsan farjoud

Despite the high success rate, implant-supported prostheses fail in some cases. Control of the applied forces is an important factor determining the success or failure of implants. Complete understanding of the biomechanical principles in implant-supported prostheses is necessary for offering an appropriate custom-made treatment plan for each patient and reducing the risk of functional complications. Finite element analysis is a quantitative method for the assessment of force distribution in complex structures. This study sought to compare the effect of different framework materials on stress distribution in bone supporting implants using three-dimensional finite element analysis. In this in-vitro study, a three-dimensional model of bone was obtained using Cone Beam Computerized Tomography (CBCT). Using CATIA V5R20 (Dassault Systemes, France) software, a NobelReplace tapered implant (Nobelpharma Co., Gothenburg, Sweden) measuring 13 mm in height and 4.3 mm in diameter was virtually inserted in the anterior maxilla. A titanium abutment, ZOE cement and superstructure with different frameworks (Ag-Pd, Ni-Cr, and fiber-reinforced composite) were designed. Force was applied in an amount of 178 N at three angulations of zero, 30 and 45° relative to the implant axis and the maximum von-Mises stress and maximum strain were calculated for cortical and trabecular bone. Changing the framework material caused a small change in level of stress and strain and their distribution pattern. By increasing the angulation of the applied force, amount of stress and strain in the implant-supporting bone increased. Maximum stress and strain were applied at 45° angulation. At zero degree angulation, maximum stress in the cortical bone was 17.326 MPa with Ni-Cr framework, 17.383 MPa with Ag-Pd and 17.321 MPa with fiber-reinforced composite. In loading at 30° angulation, maximum stress in the cortical bone was 136.95 MPa with Ni-Cr framework, 136.03 MPa with Ag-Pd framework and 136.18 MPa with fiber-reinforced composite framework. In loading at 45° angulation, maximum stress in the cortical bone was 161.37 MPa with Ni-Cr, 161.21 MPA with Ag-Pd and 160.4 MPawith fiber-reinforced frameworks. The difference between framework materials with higher and lower strengths in amount and pattern of cortical stress and strain distribution was insignificant