Comparison of stress patterns in edentulous mandibular bone around two implant retained, four implant retained overdenture and all-on-four concept - A 3 dimensional finite element analysis

Recently the use of tilted implants has been considered as a preferable option in case of atrophic edentulous arches. The tilted longer implants can be of use to ward off the important anatomical structures while also permitting cantilever reduction. Since the load transfer mechanism of an implant can be altered significantly by the number of implants and its location in the edentulous ridge, the present study evaluates and compares the stress patterns in the edentulous mandibular bone around two implant retained, four implant retained over denture and all on four concepts under different loading conditions using finite element analysis. Purpose: The biomechanical behaviour of the ‘All-On-Four’ system was compared with that of the two-implant-supported and 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 ‘All-On-Four’, 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 and the least for All-On-Four overdenture design. In all three designs, the least patterns. Thus from the study it can be concluded that the All-On-Four Concept is a clinically applicable treatment option for the atrophic edentulous ridges and induces least amount of stresses on the edentulous ridges. Therefore the overall longevity of the prosthesis is greatly enhanced.