Stress distribution on a three-unit implant-supported zirconia framework. A 3D finite element analysis and fatigue test

Abstract

Purpose: The purpose of this study was to investigate, by finite element analysis (FEA) and fatigue analysis, the influence of different loading conditions on the stress distribution in a 3-unit implant-supported Y-TZP fixed partial denture (FPD).

Material and methods: A three-dimensional FEM model was developed. The materials used in this study were assumed to be linearly elastic, homogeneous and isotropic. 100 N and 300 N loads over a 0,5 mm(2) areas with different angles (0°, 15° and 35°) and locations were applied on the prosthesis and the distribution of equivalent von Mises stress was investigated. A fatigue analysis was carried out too.

Results: Maximum stresses were found at the connector region of the framework when the intermediate element is loaded (100 N load pattern: 32,9 MPa, 33 MPa and 51,8 MPa; 300 N load pattern: 98,6 MPa, 102,8 MPa and 155,7 MPa, respectively with 0°, 15° and 35° of inclination). Results confirmed the vulnerability of both connector areas even if just one pillar was loaded with an increase in stress when angle of load inclination is larger. The cyclic fatigue evaluation indicates a strong propensity for fatigue behavior, presenting a considerable range of loading conditions. No fracture fatigue occurred with a 100 N force. A 300 N force applied to the pontic produces no fatigue problems because the load is equally shared by whole system. A 300 N force applied to one of the two pillars, or to both implants generates fatigue problems.

Conclusion: F.E.M. analysis of a 3-unit implant-supported Y-TZPFPD, give accurate information about loading conditions for clinical success over time. Fatigue analysis results show structural reliability of the Y-TZP as framework material for 3-unit posterior FPDs.

Keywords: fatigue analysis; finite element analysis; zirconia framework.

Figure 1

Three-dimensional finite element Y-TZP FPD model mesh.

Figure 2

von Mises stress values (Pa) and distributions found when the pontic load was applied: (a) 100 N – 0°; (b) 300 N – 35°.

Figure 3

von Mises stress (Pa) values and distributions found when the abutment load was applied (posterior loading): (a) 300 N – 0°; (b) 300 N – 35°. High stress rises in both connector regions also when the load is applied on one pillar abutment.

Figure 4

von Mises stress values (Pa) and distributions found in the physiological load: (a) 100 N – 0°; (b) 100 N – 15°. Connector regions show maximum stresses.

Figure 5

Distribution of von Mises Stress (MPa) under 300 N load on single element of the framework.

Figure 6

Distribution of von Mises Stress (MPa) under simultaneous 100 N load over the entire framework.