The effect of implant level in single six-support bridge-like prosthesis designs on the stress-strain state of structural elements based on three-dimensional mathematical modeling

Abstract

Objective. To evaluate the stress-strain state of bone tissue supported by six dental implants under various types of occlusal loading by finite element analysis. Materials and methods. A three-dimensional finite element model of the mandibular segment with six implants and a fixed bridge prosthesis was developed. The properties of cortical and cancellous bone and titanium implants were modeled. The analysis was performed using the von Mises stress criterion to assess equivalent stresses in the bone, implants, and prosthesis. Results. The finite element method was used to evaluate the implant–bone system under various occlusal loads. Under a 500 N load on the incisors, the maximum von Mises stresses in the implants were 550.8 MPa (position 4.2) and 523.7 MPa (position 3.2), with displacements up to 0.109 mm. Under an 800 N load on the molars, the stresses in the implants reached 591.3 MPa (position 4.6) and 545.1 MPa (position 4.4), with displacements of 0.049 mm and 0.028 mm, respectively. In the bone tissue surrounding the implants under the 500 N load, the average stresses ranged from 8.8 MPa (position 4.2) to 18.9 MPa (position 3.2). The modeling accounted for the difference between cortical and cancellous layers through the finite element mesh. Conclusions. Thus, three-dimensional finite element analysis enabled quantitative assessment of the stress–strain state of a six-implant-supported fixed dental prosthesis, with the implants placed at different levels. The distribution of equivalent stresses and displacements was markedly non-uniform. Under each loading condition, the highest stresses were recorded in the implant placed 3 mm deeper than the adjacent implant.