Finite Element Analysis Of Four-units Loss In Maxillary Anterior With Different Implant-supported Cantilever Fixed Dental Prostheses

Objective:To evaluate the stress distribution of alveolar bone around the implant,implant and abutment when using three different implant-supported cantilever fixed dental prostheses for four-units missing in maxillary anterior by three-dimensional finite element analysis,we can provide some theoretical reference for the use of cantilever implant-supported fixed dentures for four-units missing in maxillary incisor area clinically.Methods:The CBCT images provided by a volunteer who met the recruitment conditions was imported into Mimics software for three-dimensional reconstruction,and the models of maxillary bone and dental crown were obtained.Referring to the parameters of SIC implant system,Catia software was used to draw the models of implant,abutment and abutment screw.After completing the processing and optimization of each part of the model by Geomagic Wrap software,the precise assembly of the whole model is completed by Catia software.A total of 40 sets of models were tested by simulating three kinds of prosthetic methods(A: cantilever fixed bridge supported by three implants,B: single-end cantilever fixed bridge supported by two implants,and C: double-end cantilever fixed bridge supported by two implants),different implant diameters(3.0mm,3.5mm),lengths(6mm,9.5mm,11.5mm),and abutment materials(titanium abutment and zirconia abutment).Ansys finite element software was used to analyze the stress of the model,which applied a force at an angle of 30 to the crown at the junction between the lingual 1/3 and the middle 1/3 of the four maxillary incisor with a dispersive load of 50 N.The normal form equivalent stress distribution of alveolar bone,implant and abutment of each group model after stress was obtained by Ansys software operation,and the corresponding maximum equivalent stress value was recorded for comparative analysisResults:1.The maximum equivalent stress values of the alveolar bone,the implant and the abutment in the 40 groups of models were within their respective yield strengths.Among the three types of cantilever implant fixed denture,the stress distribution of alveolar bone in repair method A is more dispersed,followed by repair method C,and the stress of alveolar bone in repair method B is more concentrated.2.In the same restoration design way,as the diameter of the implant increases,the maximum equivalent stress value of the alveolar bone and the implant subsequently decreases,and that of the abutments subsequently increases.As the length of the implant increased,the maximum equivalent stress value of alveolar bone in the 3.5mm diameter group decreased,and that of the implant and the abutments increased;However,in the3.0mm diameter group,the maximum equivalent stress changes of all three were not obvious,and when the short implant was used at the end far from the cantilever,the maximum equivalent stress of the alveolar bone decreased slightly,the maximum equivalent stress of the implant significantly decreased,and the maximum equivalent stress of the abutment significantly increased.3.By increasing the number of implants,the maximum equivalent stress of alveolar bone in the 3.0mm diameter group of repair modality A could be reduced substantially,approaching that of the 3.5mm diameter group of repair modality C and significantly smaller than that of the B mode.4.The maximum equivalent stress values of the alveolar bone and the implant in the zirconia abutment group were lower than that in the titanium abutment group under the same conditions.The maximum equivalent stress value of the abutment is obviously larger than that of the titanium abutment group under the same condition.Conclusions:1.Under the present experimental conditions,three kinds of implant-supported cantilever fixed denture restoration methods are feasible,and the stress distribution of alveolar bone in restoration method A is more dispersed.2.The increase in the diameter of the implant is positive for reducing the stress in the alveolar bone around the implant.The effect of diameter on the stress values of alveolar bone,implant and abutment was more significant than that of length.3.In narrow diameter implants,the effect of length modification on the von-Mises peak stress of alveolar bone,implants as well as abutments is limited.In the 3.5mm diameter group,the stress in the alveolar bone could no longer be reduced substantially when the implant length exceeded 9.5 mm.4.Zirconia abutment can make the stress distribution of alveolar bone more uniform.In order to achieve better aesthetic restoration effect,zirconia abutment can be used to repair the four-unit defect of maxillary incisor area.