IADR Abstract Archives
Effect of Firing Time on the Biaxial Strength of 3D-Printed Zirconia
Objectives: This study should clarify if fast overnight firing is possible for thin-walled 3D-printed zirconia objects without a drastic reduction in material strength.
Methods: Samples for biaxial strength testing (diameter 12.4 mm) were printed from a slurry containing zirconia particles (LithaCon 3Y 210). After cleaning the samples, half of the samples underwent an overnight firing (14.5h) whereas the other half was fabricated using a long firing program (51h). Each half of the specimens possessed a (nominal) sample thickness of 0.6 mm and 1.2 mm respectively. Thus, there were 4 subgroups (n=38/group) combining the two factors “specimen thickness” and “firing time”.
Before biaxial strength testing according to ISO 6872, samples were only exhibited to sandblasting (Al2O3, 0.1MPa). With the measured individual specimen dimensions and the maximum load during the fracture tests, biaxial strength values could be calculated for each specimen.
Mean values and standard deviations as well as the Weibull parameters (characteristic strength σ0, Weibull modulus m) were calculated for each test group. Kruskal-Wallis and pairwise Mann-Whitney U-tests served to detect significant differences between the test groups.
Results: Biaxial strength was highest for the samples that underwent a long firing with no significant difference between 0.6 mm thick samples (σ=1057±211 MPa, σ0=1043MPa, m=5.8) or 1.2 mm thick samples (σ=1158±112 MPa, σ0=1166MPa, m=2.4). Overnight fired samples had a reduced strength for 0.6 mm thickness (σ=992±267 MPa, σ0=1089MPa, m=4.3) and 1.2 mm thickness (σ=805±527 MPa, σ0=899MPa, m=1.4) respectively. However, only the decrease in material strength for the 1.2 mm thick samples was significant (p<0.001).
Conclusions: Thin 3D printed zirconia discs can be sintered overnight without impairing the material strength.
Methods: Samples for biaxial strength testing (diameter 12.4 mm) were printed from a slurry containing zirconia particles (LithaCon 3Y 210). After cleaning the samples, half of the samples underwent an overnight firing (14.5h) whereas the other half was fabricated using a long firing program (51h). Each half of the specimens possessed a (nominal) sample thickness of 0.6 mm and 1.2 mm respectively. Thus, there were 4 subgroups (n=38/group) combining the two factors “specimen thickness” and “firing time”.
Before biaxial strength testing according to ISO 6872, samples were only exhibited to sandblasting (Al2O3, 0.1MPa). With the measured individual specimen dimensions and the maximum load during the fracture tests, biaxial strength values could be calculated for each specimen.
Mean values and standard deviations as well as the Weibull parameters (characteristic strength σ0, Weibull modulus m) were calculated for each test group. Kruskal-Wallis and pairwise Mann-Whitney U-tests served to detect significant differences between the test groups.
Results: Biaxial strength was highest for the samples that underwent a long firing with no significant difference between 0.6 mm thick samples (σ=1057±211 MPa, σ0=1043MPa, m=5.8) or 1.2 mm thick samples (σ=1158±112 MPa, σ0=1166MPa, m=2.4). Overnight fired samples had a reduced strength for 0.6 mm thickness (σ=992±267 MPa, σ0=1089MPa, m=4.3) and 1.2 mm thickness (σ=805±527 MPa, σ0=899MPa, m=1.4) respectively. However, only the decrease in material strength for the 1.2 mm thick samples was significant (p<0.001).
Conclusions: Thin 3D printed zirconia discs can be sintered overnight without impairing the material strength.