Influence of implant number and various prosthodontic designs on biomechanical behaviors of the implant-supported fixed denture in posterior mandible: A 3D finite element study

Abstract

1. Purpose

The purpose of this study was to evaluate the biomechanical behaviors of implant-supported fixed prostheses with various designs and different number of implants at mandibular posterior region using 3D finite element analysis.

2. Material and methods

Finite element models consisting of partially edentulous mandible at posterior region, remaining teeth, implant system (Osstem US system

Osstem Implant Co.) and prostheses were created based on the patients computed tomographic data. Four models with the variations were constructed as follows: four implants from first premolar to second molar with non-splinted crowns (NS)

four implants with splinted crowns (SP)

three implants at first and second premolar and second molar with pontic (PT)

two implants at first premolar and first molar with cantilever design (CT). The frictional coefficient of 0.3 was set among the interfaces of implant system with 825 N of preload at the implant screw. An oblique force of total 300 N at an 11.3-degree angle to the long axis of the implant was applied to the occlusal surfaces of the crowns. The von Mises stress and displacement of each component in the models were evaluated.

3. Results

The results showed that the von Mises stress in implant significantly increased as the number of implants used in the models were decreased, mainly for the cantilever design (577.7 MPa in model NS, 616.8 MPa in model SP, 649.3 MPa in model PT and 791.6 MPa in model CT). On the contrary, cantilever model showed less stress than other models in cortical bone and crowns (112.2 and 220 MPa respectively). A non-splinted model resulted in less stress than splinted one in the components such as cortical bone and implant (151 and 577.7 MPa in model NS, 182.3 and 616.8 MPa in model SP) However, lower stresses were observed in cancellous bone and crowns for splinted model (31.9 and 297.7 MPa in model SP, 36.8 and 298.4 in model NS).

4. Conclusion

The reduction of the number of implants suggested higher stress concentration in certain components of implant-supported fixed prostheses. However, there was no significant relation between the stress concentration and the number of implants in other components such as bone or crowns. Thus, applying pontic or cantilever designs could be also acceptable as treatment planning options.