The Influence Of The Unique Design Of Two Implant Systems On The Stress Distribution Analyzed By The Three Dimensional Finite Element Method

Objective To study the stress distribution of various components of Thommen and Astra implant systems with unique design method under external load.Evaluate the advantages and disadvantages of implant thread design and implant-abutment connection mode in stress dispersion,and the feasibility of ultra-fine screw design.Providing reference for the design of implant system.To explore the relationship between stress distribution and tightening torque of Thommen connecting screws,and to guide clinical practice.Methods 1.Model building:Data collection of all components of the two implant systems and maxillary data acquisition.The three dimension model of tooth-implant-maxillary system was established by three dimension software.2.Stress distribution analysis:assign values to the properties of each material,define the binding contact relationship between each component,then conduct mesh division,define boundary conditions,set the tightening torque of the connecting screw,and apply loads on the upper crown:200N loads in the vertical direction,100N loads in the horizontal direction and 150N loads in the oblique direction of 45°.The stress distribution of each part of the dental-implant-maxillary system was analyzed by three-dimensional finite element method.3.Set different tightening torque for the connecting screw of Thommen planting system to explore the relationship between the stress distribution of the connecting screw and the tightening torque.Results 1.Under external loading,abutment stress was concentrated on the abutment junction of implant.Thommen connecting screws stress is mainly concentrated on the upper primary thread and smooth section.Astra connecting screws stress is concentrated on the upper primary thread with smooth segment transitions.The upper thread implant stress concentrated on implant neck.Prompt is the weak part of stress under the action of these positions.2.Astra implant were designed with v-thread and neck micro-thread.Thommen implant were designed with trapezoidal thread.The stress peaks of Astra implant at stress concentration were smaller than Thommen.3.Under external loading,the stress concentration range of Thommen abutment is smaller than that of Astra abutment.And the stress peak at the stress concentration location is much lower than that of Astra.4.Under external loading,the stress peak of Thommen 1.6mm connecting screw was much higher than that of Thommen 1.9mm and Astra 2.3mm connecting screw.The stress peak of Thommen 1.9mm connecting screw was similar to Astra 2.3mm.The stress concentration position of the connecting screws of the two implant systems is the smallest diameter position.5.Under external loading,the equivalent stress and the peak value of the maximum principal stress of the connecting screw increase linearly with the tightening torque.Conclusion 1.The components of the implant system were designed to be improved and strengthened in weak positions.2.Implant thread design,v-shaped thread combined with neck micro thread design can better disperse stress.3.The design of the implant-abutment connection can adopt internal and external double connection,which can greatly disperse the stress on the abutment.4.The place with the smallest diameter of the connecting screw is the place with the peak stress concentration.The diameter of the connecting screw should not be super fine.5.In clinical work,we should strictly follow the manufacturer’s instructions to tighten the connecting screw.