3-D Finite Element Analysis Study Of Implant Supported Longitudinal Removable Partial Dentures:Relationship Between Number And Location Of Osseointegrated Implant And Stress Distribution

Purpose The purposes of the study were to evaluate the evaluate the biomechanical behavior of a mandibular distal extension removable partial denture associated with an implant,including its different location on stress values and stress distribution within bone,alveolar mucosa,and implant,as well as on the displacement of alveolar mucosa and RPD.by bidimensional finite element method.Materials and methods The 3-dimensional finite element analysis method was selected to evaluate the stress values,distribution and displacement in six geometric 3-D models which were prepared by FEM software package and CT scan of patient mandible,composed of: mandibular,alveolar mucosa,nature tooth and distal extension RPD with implant support.All implants have the same Specifications 4.1 *10 mm.Sixteen mandible models were simulated: Model 1.blank control without implant denture;model 2.control group for conventional partial denture restoration;model 3～6for partial denture restoration supported by implant,the number of implants was 1,followed by #4,#5,Models #6,#7;Models 7-12 are still implant-supported longitudinal partial dentures with a number of implants of 2,including two implants located in all locations in the edentulous area.;50 N vertical forces were utilized as load cases.Stress distribution and Von Mises stress values were assessed for simulated tissues and implants.Also 3-D displacement of alveolar mucosa RPD were evaluated using FEM software.Results1.1.With or without implant support,stress concentrations occur in the buccal side of the alveolar ridge in the premolar area.2.Using implants to support RPD can reduce the Von Mises stress on the cortical bone and alveolar mucosa,and reduce the deformation of the denture and alveolar mucosa,and increase the maximum Von Mises stress of the cancellous bone under load.3.Under the functional load,the denture is prone to uneven deformation,and it appears in the near middle retainer.With the support of the implant,the denture displacement is reduced and the deformation is uniform.4.As the implant position moves to the far side,support for the premolar area is gradually reduced,and support for the molar area is enhanced.The implant bears most of the resultant force under functional loading.5.When the two implants are concentrated in the molar area,the cortical bone stress is reduced;when the two implants are concentrated in the premolar area,the cortical bone stress increases.6.Use two implants to support situations where their own force is greater than one support.7.Increase implant support at specific locations to effectively reduce tissue forces and displacement.Conclusions 1.The support of the implant reduces the burden of the abutment while making the resultant force distribution more uniform.In the premolar area,the implant effectively disperses the force and reduces the stress value of the cortical bone;in the molar area,the cortical bone bears more force and the implant is protected.2.When the two implants were #6,#7,the cancellous bone,cortical bone,mucosa and implant,and the card ring were the smallest in all groups,and the implant was most protected at this position.#6,#7 in all experimental groups are the best design locations.