Three-dimensional Finite Element Analysis Of Implant Site Selection Of Mandibular First Molar With Mid-inclined Second Molar After Loss Of Mandibular First Molar

Three-dimensional finite element analysis of the choice of dental implant site when the mandibular second molar is near-median inclination and the first molar is missing.OBJECTIVE: To study the stress distribution characteristics of implants,abutments,crowns,cortical bones and cancellous bones at different implant sites under loading conditions,using three-dimensional finite element analysis(FEA)under the condition that the mandibular second molar is near-median inclination and the second premolar is in normal position after the first molar is missing.Providing a certain theoretical reference to clinical work.Methods: 1.The geometric models of mandibular bone block,implant,abutment and crown were drawn by ANSYS.2.The mandibular second molar was simulated to be inclined to 30 degrees near the middle,and the appropriate size of crown was designed according to the residual space.3.Establish three-dimensional finite element models of crowns and implants at different implant sites,and compare the stress of implants,abutments and alveolar bones under the same load.Results:Results:Three-dimensional finite element analysis experiments were carried out to obtain the stress distribution nephogram when the axis of implant and the middle axis of crown deviated from different distances under the same load.The results showed that Von Mises stress was smaller when the implant axis was not deviated from the crown axis under 150 N static load perpendicular to the crown and maxillofacial surface,and mainly concentrated at the junction between the implant and the abutment and the cortical bone around the implant.The stress of cancellous bone was uniform.When the axis of the implant deviates from the central axis of the crown,the maximum Von Mises stress mainly concentrates on the proximal-middle junction of the implant and the abutment and the proximal-middle cortical bone of implant,and the cancellous bone is evenly stressed.As the distance between the implant axis and the crown axis increases,the Von Mises stress peak value of implant,abutment and cortical bone increases,while the Von Mises stress value of cancellous bone does not change significantly.When the axis of implant deviates from the crown axis 0-0.75 mm,the maximum Von Mises stress increases steadily at the proximal-middle junction of implant and abutment and the cortical bone around the implant.When the axis of implant deviates from the crown axis 0.75-1.25 mm,the maximum Von Mises stress increases significantly at the proximal-middle junction of implant and abutment,and the stress changes of cancellous bone are not obvious.The stress of implant and abutment under load is much greater than that of cortical bone and cancellous bone.Conclusions:After the loss of the first mandibular molar,the central axis of the implant deviates from the central axis of the crown under the condition that the second mandibular molar is nearly 30 degrees inclined and the position of the second premolar is normal.The crown and implant forms a cantilever beam of different lengths,which increases the maximum Von Mises stress on the implant,abutment and surrounding cortical bone.With the increase of the deviation distance,the implant,abutment and surrounding skin will be increased.The maximum Von Mises stress on the bone tends to increase.The stress of alveolar bone around the implant is reduced,but the stress of the junction of the implant and the abutment increases,which increases the burden of the implant and abutment.Therefore,there is a risk of deformation and fracture at the implant and abutment.Cantilever beam should be avoided between the crown and the implant in clinical work,and the implant site should be selected reasonably to reduce the stress,which will ensure the long-term stability of implants and improve the success rate of implants.