Three-dimensional finite element analysis of two-implant-supported locator overdenture in different reinforced denture base designs under four loading conditions

This study used three-dimensional (3D) finite element analysis to compare the effect of different reinforcement designs, including strengthening metals and fiberglass.in overdentures supported by two canine implants to restore edentulous mandibles. The von Mises equivalent stress (VMES) and the maximum and minimum principal strains were used to evaluate the stress distribution in the implants and denture bases of eight 3D finite element models in different reinforced denture base designs under four different working conditions, including the vertical occlusal force of the anterior (F4) and posterior teeth (F1) and the lateral occlusal force (F2, F3) of the posterior teeth. Under F1 loading, the stress concentration area and VMES in the MP (Internal strengthening metal plate) and MP-F (Internal strengthening metal plate with fiberglass in buccal base) models decreased significantly (from 0.53 MPa to 0.43 and 0.46 MPa). Under F2 and F3 loading, the addition of a metal framework resulted in a lingual central stress concentration area located away from the base edge transition, with a uniform overall distribution and a reduced lingual stress concentration area of the implant. In MP and MP-F models, the VMES and maximum stress were significantly reduced (1.27 MPa, 1.21 MPa and 1.40 MPa, 1.20 MPa). The labial fiber reinforcement bundle for MP-F strengthened the local structure, reduced the local maximum stress value, and promoted local stress distribution.Under F4 loading, the stress in all eight models was located at the alveolar crest of anterior teeth. In overdentures supported by two canine implants to restore edentulous mandibles, the addition of a metal plate within the lingual base significantly reduced the denture and implant stress concentration areas, as well as the VMES of the denture and implant. It also reduced the maximum stress of the denture and implant under lateral occlusal, locally strengthened the fracture resistance of the denture base, and reduced the incidence of implant neck fracture, particularly with E-fiber strengthening of the labial base. This study corroborates that the base of the implant overdenture with 2 implants in the lower jaw can be reinforced by designing lingual metal plates and labial fibers.