Method: Disc-shaped specimens (12mm x 2mm and 12mm x1mm) were prepared according to manufacturer's recommendations. The flexural strength was determined by biaxial flexure test for the control groups. The ageing protocol involved frequency of 2 Hz and 1 million cycles. Stress levels were 48 MPa for 2mm-thick specimens and 193 MPa for 1mm-thick specimens. After aging, specimens were tested in biaxial flexure. Statistical analysis was performed with Student’s t test (alpha=0.05).
Result: The results are presented in the table. Aging specimens in a chewing simulator reduced the strength of the Y-TZP for both stress levels tested (1 and 2 mm-thick specimens), however these differences in strength were not statistically significant. An increase in the coefficient of variation was observed after mechanical cycling for both specimen’s thicknesses.
Thickness |
Condition |
σmean (MPa) |
σmin (MPa) |
σmax (MPa) |
p-value |
2 mm |
Control |
856.1 ± 76.0 (9%) |
773.5 |
971.2 |
0.37 |
Cycled |
816.8 ± 111.9 (14%) |
604.4 |
1003.9 |
||
1 mm |
Control |
786.1 ± 96.5 (12%) |
613.0 |
966.9 |
0.66 |
Cycled |
759.5 ± 174.6 (23%) |
531.4 |
1121.6 |
Conclusion: A variation in the stress level from 48 to 193 MPa does not affect the strength degradation of Y-TZP discs after chewing simulation at 2 Hz and 1 million cycles.
Keywords: Ceramics and Mechanical cycling