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The objective of this study was to investigate the influence of implant/abutment joint designs on abutment screw loosening in a dental implant system, using nonlinear dynamic analysis of the finite element method (FEM). This finite element simulation study used two dental implant systems: the Ankylos implant system (Degusa Dental, Hanau, German) with a taper joint (taper joint-type model), and the Bränemark implant system (Nobel Biocare, Gothenburg, Sweden) with an external hex joint (external hex joint-type model). The nonlinear dynamic analysis was performed using three-dimensional finite element analysis. In comparing the movement of the taper type-joint model and external hex type-joint model, it was found that the external hex type-joint model had greater movement than the taper type-joint model. The external hex joint-type model showed rotation movement, whereas the movement of the taper joint-type model showed no rotation. It was concluded that the nonlinear dynamic analysis used in this study clearly demonstrated the differences in rotation of components in dental implant systems with taper or external hex joints.

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Using finite element method (FEM) , this study sought to investigate how the thickness and Young's modulus of cortical bone influenced stress distribution in bone surrounding a dental implant. The finite element implant-bone model consisted of a titanium abutment, a titanium fixture, a gold alloy retaining screw, cancellous bone, and cortical bone. The results showed that von Mises equivalent stress was at its maximum in the cortical bone surrounding dental implant. Upon investigation, it was found that maximum von Mises equivalent stress in bone decreased as cortical bone thickness increased. On the other hand, maximum von Mises equivalent stress in bone increased as Young's modulus of cortical bone increased. In conclusion, it was confirmed that von Mises equivalent stress was sensitive to the thickness and Young's modulus of cortical bone.

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