Three-dimensional Finite Element Analysis Of Bone Stress Changes Under Different Design Schemes Of All-on-Four Maxillary Standard Type

Objective : By comparing the changes in bone stress under different design schemes,to decide how to choose the appropriate implant tilt angle and the cantilever length of the upper prosthesis in the case of non-axial implantation of All-on-four,so as to maximize reduce the stress of the bone tissue around the implant to a certain extent, increase the survival rate of the patient’s denture.Material and Method: Establish separately anterior vertical,anterior mesial,and anterior far implant plans with different angles and load 50 N from the right implant distal 2mm,4mm,6mm,10 mm to the most distal center of the superstructure area,and set the load on the implant here to be at its maximum.Comparing the relevant data in different design schemes through three-dimensional finite element models,including maximum principal stress(maximum principal,smax),minimum principal stress(minimum principal,smin)and von Mises(von Mises,sv M)stress values.Results: 1)The peak stress of the vertical implantation of the anterior two implants was the smallest,and the peak value of the proximal oblique implantation of the anterior two implants was smaller than that of the distal oblique implantation of the anterior two implants;2)The peak value of the distal oblique implantation of the anterior two implants was smaller than that of the distal oblique implantation of the two implants.two.In the same model,the larger the angle,the smaller the stress.;3)In the comparison between the model of anterior implant tilt of 15 °and that of anterior implant tilt of 30 °,it was found that the difference of stress value was negligible.4)From the point of view of stress level,in the same model,the bone stress around the implant was the lowest in the 40 °model.;5)In all load simulations,the maximum stress is always found at the neck of the distal implant.With the increase of the inclination,the stress of the distal implant increases in the top direction.The stress locations and distribution patterns between the evaluation models are very similar;6)The increase of the inclination of the distal implant is proportional to the increase of stress concentration.Compared with the other two models,the 40 °model produced higher stress at the bone-implant interface(especially at the distal end),and the increase of distal implant length did not significantly change the stress distribution and magnitude.40 °inclination of distal implant is more beneficial to stress dispersion than 30 °inclination.Conclusion: The use of the elongated All-on-four grafting plan with a larger angle can significantly reduce the stress distribution of the surrounding fracture.It can be further verified and promoted clinically.