Fatigue behavior of zirconia under different loading conditions

Abstract

Purpose: To investigate the influence of surface damage on the fatigue behavior of zirconia under two different loading conditions.

Materials and methods: One hundred twenty zirconia bar-shaped received either airborne particle abrasion using 50μm or 120μm alumina particles while polished specimens served as control. The specimens were subjected to two fatigue regimes: dynamic fatigue (1,000,000 cycles, 1hz and 0.5s contact time) or static fatigue (a constant load applied for 5000s) under water using the staircase application of the load. The flexure strength after fatigue (dynamic fatigue strength) was compared to the initial flexure strength of the tested specimens (α=0.05). The critical crack shape and size of fractured specimens was examined using scanning electron microscopy.

Results: Compared to the initial flexure strength of the tested specimens, dynamic fatigue strength was 86.3% for the polished specimens, 73.4% for 50μm particle abrasion, and 42.3% for 120μm particle abrasion while the static fatigue strength was 85.9%, 78.5%, and 51.5% respectively. Significant statistical differences (F=223.679, P<0.001) were found between different surface treatments but not between dynamic and static fatigue strengths for the same type of surface treatment.

Conclusions: The dynamic and static fatigue strengths of zirconia are significantly influenced by type of surface damage.

Clinical implications: Within the limitations of this study, surface damage have great influence on fatigue behavior of zirconia.

Keywords: Cyclic loading; Dynamic; Fatigue; Residual strength; Static; Zirconia.