Effects of abutment screw preload in implant connection systems: A 3D finite element study
Zhiyan Jin, Prof. Ho-Beom Kwon, Dr. Mary Delia Z. Bondoc, Mi-EL Kim
Seoul National University School of Dentistry
Objectives
The purpose of this FEA study was to evaluate and verify the effects of the presence of the preload condition on abutment screws under the occlusal load for internal hexagonal connection systems.
Materials and Methods
The finite element models consisting of bone blocks, implant systems (BlueDiamond®, MegaGen, Daegu, Korea), and crowns were created. With these components, a total of 2 models with different conditions were constructed for FEA: internal hexagonal system with preload (Model 1) , internal hexagonal system without preload (Model 2). An 11.3-degree oblique load (100 N) to the axis of the implant was applied on the occlusal surface of the crown for the models with occlusal load. A preload of 300 N was applied in the abutment screw of the model1. The maximum von Mises stress, maximum principal stress, and maximum displacement of the components of the models were evaluated.
Results
Among the components, the abutment screw showed the greatest increase under occlusal load in the von Mises stress values with preload conditions between 274 MPa in the model 1 and 13 MPa in the model 2. Regardless of the preload condition, the implant showed the highest stress values of all parts, followed by the abutment. When comparing the internal hexagonal system with preload and the internal hexagonal system without preload, the maximum stress values of the internal hexagonal system with preload (Model 1) were higher in the screw, crown, ZrGen Aubtment (274, 47, 260 MPa in the model 1 and 13, 46, 33 MPa in the model 2). For both connection systems, irrespective of the preload or occlusal load, the smallest stress values were obtained in cancellous bone (1.68 MPa in the model 1 and 1.68 MPa in the model 2), followed by cortical bone (20 MPa in the model 1 and 20 MPa in the model 2).
Conclusions
The presence of a preload condition significantly affected the biomechanical behaviors of the components of 2 systems. The preload condition should be included in FEA to achieve more realistic results.