The comparative evaluation of stress distribution in porous tantalum implant and solid titanium implant assisted All-on-four’ prosthesis, in maxillary bone, using three- dimensional finite element analysis method

Abstract

Objectives: This study aimed to assess the stress distribution pattern in all-on-four maxillary restorations supported by porous tantalum and solid titanium implants using three-dimensional (3D) finite element analysis (FEA). Materials and Methods: In this FEA, a geometric model of an edentulous maxilla was designed. Zimmer screw-shaped tantalum and solid titanium implants were also modeled. Four implants (2 mesial implants, and 2 distal implants with 0, 15, 30, and 45-degree distal tilting) were used to design an all-on-four restoration. Four models with the all-on-four concept were designed as such. The fifth model had 6 vertical implants (all-on-six). Two different implant types (porous tantalum and solid titanium) were modeled to yield a total of 10 models, and subjected to 200 N bilateral vertical load and 150N, 30° inclined force linguo-buccally. Pattern of stress distribution and maximum von Mises stress values in cancellous and cortical bones around implants were analyzed. Results: In tantalum models subjected to 200 and 150N loading, the effect of increasing the distal tilting of posterior implants and subsequent reduction in cantilever length was comparable to the effect of increasing the number of implants to 6 on von Mises stress values in cortical bone. However, in cancellous bone, a more significant difference was observed and the effect of increasing the tilting of posterior implants and subsequent reduction in cantilever length on stress reduction was slightly greater than the effect of increasing the number of implants to 6. In solid titanium models subjected to 200N loading, the effect of both of the abovementioned parameters was comparable on stress values in cancellous bone; but in cortical bone, the effect of increasing the implant number was slightly greater on stress reduction. In solid titanium models subjected to 150N loading, in both cortical and cancellous bones, the effect of increasing the distal tilting of posterior implants and subsequent reduction in cantilever length on stress values has no significant difference with the effect of increasing the number of implants to 6 and the both are critical factors for stress reduction. Conclusion: Despite similar pattern of stress distribution in bone around porous tantalum and solid titanium implants, higher maximum von Mises stress values around tantalum implants indicate higher stress transfer capacity of this type of implant to the adjacent bone, compared with solid titanium implants.