IADR Abstract Archives
Effect of accelerated aging on flexural strength of two yttria-stabilized tetragonal zirconia
Objectives: The objective of the current study was to evaluate the effect of accelerated aging on flexural strength of conventional and translucent commercially available yttria-stabilized tetragonal zirconia polycrystalline (Y-TZP) materials from the same manufacturer
Methods: Forty thin bars (22x3x0.3 mm) of green stage Y-TZP, 20 from conventional Cerec inCoris ZI (ZI) and 20 from translucent zirconia Cerec inCoris TZI (TZI), were sintered according to manufacture instructions. Ten specimens from each material were evaluated after sintering. The remaining ten specimens were artificially aged at standard autoclave sterilization conditions 134˚C at 0.2 MPa for 5 hours (AZI, ATZI). Tetragonal to monoclinic transformation due to accelerated aging was measured with X-ray diffraction (XRD) for 3 specimens from each group. The flexural strength of the specimen was determined by -3 point bending test in a universal testing machine. Before each measurement, specimen dimensions were measured with a digital caliper with minimum thickness 0.3±0.01 mm. Mean values of flexural strength (MPa) were calculated. Data were analyzed as a function of material and aging. Tow-way ANOVA test was used to compare the mean flexural strength of the aged specimens with that of the non aged ones
Results: The mean value of the flexural strength± SD were: 1515±101 MPa ( ZI), 1405 ± 78 MPa (TZI), 1355 ± 88 MPa (AZI), and 1345 ± 70 MPa (ATZI). The XRD peak intensities before aging showed that there was no monoclinic phase detected in both types of zirconia. After aging, the relative XRD peak intensities showed that there was a monoclinic transformation in both types where the ZI specimens showed 80.4 % monoclinic phase and the TZI specimens showed 51% monoclinic phase
Conclusions: Accelerated aging caused a decrease in flexural strength of the two used types of zirconia with the degree of monoclinic transformation, and hence the decrease in flexural strength, was less in TZI than that of ZI
Methods: Forty thin bars (22x3x0.3 mm) of green stage Y-TZP, 20 from conventional Cerec inCoris ZI (ZI) and 20 from translucent zirconia Cerec inCoris TZI (TZI), were sintered according to manufacture instructions. Ten specimens from each material were evaluated after sintering. The remaining ten specimens were artificially aged at standard autoclave sterilization conditions 134˚C at 0.2 MPa for 5 hours (AZI, ATZI). Tetragonal to monoclinic transformation due to accelerated aging was measured with X-ray diffraction (XRD) for 3 specimens from each group. The flexural strength of the specimen was determined by -3 point bending test in a universal testing machine. Before each measurement, specimen dimensions were measured with a digital caliper with minimum thickness 0.3±0.01 mm. Mean values of flexural strength (MPa) were calculated. Data were analyzed as a function of material and aging. Tow-way ANOVA test was used to compare the mean flexural strength of the aged specimens with that of the non aged ones
Results: The mean value of the flexural strength± SD were: 1515±101 MPa ( ZI), 1405 ± 78 MPa (TZI), 1355 ± 88 MPa (AZI), and 1345 ± 70 MPa (ATZI). The XRD peak intensities before aging showed that there was no monoclinic phase detected in both types of zirconia. After aging, the relative XRD peak intensities showed that there was a monoclinic transformation in both types where the ZI specimens showed 80.4 % monoclinic phase and the TZI specimens showed 51% monoclinic phase
Conclusions: Accelerated aging caused a decrease in flexural strength of the two used types of zirconia with the degree of monoclinic transformation, and hence the decrease in flexural strength, was less in TZI than that of ZI