Three dimensional finite element stress analysis of two and four implant supported prosthesis

Purpose: The biomechanical behavior of the two-implant-supported overdenture was compared with that of four-implant supported mandibular overdenture using the three dimensional finite element method (FEM). Thereby evaluating the von Misses stresses induced on the implants under different loading simulations. Materials & Method: Three dimensional models representing mandible restored with two-implant-supported and four-implant-supported prosthesis were developed in the three dimensional design software and then transferred into FEM software. The models were then subjected to four different loading simulations (full mouth biting, canine disclusion, load on cantilever, load in the absence of cantilever). The maximum von Mises stresses were localized and quantified for comparison.¹ Results: Among the three models, under all loading simulations, the maximum stress concentrations were along the neck of the implant. The stress levels for full mouth loading simulation was highest for two implant supported overdenture design when compared with the four implant retained overdenture design. In both the designs, the least stress was when the implants were loaded in a lateral direction. The stress levels for cantilever and non-cantilevered designs were nearly the same for all the simulated designs. Conclusion: When tested under different loading simulations, both models showed similar location and distribution of stress patterns. Thus from the study it can be concluded that the four implant retained over denture design is a better treatment option for the atrophic edentulous ridges and induces comparatively less amount of stresses on the edentulous ridges. Therefore the overall longevity of the prosthesis is greatly enhanced.