IADR Abstract Archives
Effect of Sintering Methods on Microstructure, Strength, Translucency of Zirconia
Objectives: Identify the effects of sintering conditions on grain size and translucency of properties of Y-TZP (Yttrium oxide partially stabilized Tetragonal Zirconium dioxide Polycrystalline).
Methods: A cylindrical Lava frame zirconia (3M ESPE) was sectioned into 30 disk-shape specimens, 25 mm in diameter and 1.25 mm of thickness.The specimens were randomly divided into two groups and sintered in the similar experimental conditions except for covering the crucibles during the sintering process. One group was left uncovered during the heat treatment, while the other group was covered. The sintering was conducted at the maximum temperature of 1530 °C for two hours. Contrast ratio (CR) of final samples was measured by spectrophotometer. Scanning electron microscopy (SEM) was further used to measure the grain size of obtained samples. Biaxial flexural strength was measured using Instron 5565A with a ball-on-three-ball setting according to ISO 6872. Data were analyzed using t-test for two groups of samples to detect significant difference (p<0.05).
Results: Sintering zirconia in the covered group significantly decreased the grain size. The mean grain size for the uncovered group was calculated to be around 0.75±0.26 µm, while for specimens sintered covered was approximately 0.65±0.025 µm (p<0.001). Additionally, the grain size distribution of the uncovered group was wider than that of the covered group. The mean CR of the uncovered group was 69.96% which increased to 70.96% for the second group specimens (p=0.035). There were, however, no significant differences in biaxial flexural strength between the two groups using t-test.
Conclusions: Sintering Zirconia in the covered and uncovered crucibles showed different grain size, distribution, and CR. There was no significant difference in biaxial flexural strength.
Methods: A cylindrical Lava frame zirconia (3M ESPE) was sectioned into 30 disk-shape specimens, 25 mm in diameter and 1.25 mm of thickness.The specimens were randomly divided into two groups and sintered in the similar experimental conditions except for covering the crucibles during the sintering process. One group was left uncovered during the heat treatment, while the other group was covered. The sintering was conducted at the maximum temperature of 1530 °C for two hours. Contrast ratio (CR) of final samples was measured by spectrophotometer. Scanning electron microscopy (SEM) was further used to measure the grain size of obtained samples. Biaxial flexural strength was measured using Instron 5565A with a ball-on-three-ball setting according to ISO 6872. Data were analyzed using t-test for two groups of samples to detect significant difference (p<0.05).
Results: Sintering zirconia in the covered group significantly decreased the grain size. The mean grain size for the uncovered group was calculated to be around 0.75±0.26 µm, while for specimens sintered covered was approximately 0.65±0.025 µm (p<0.001). Additionally, the grain size distribution of the uncovered group was wider than that of the covered group. The mean CR of the uncovered group was 69.96% which increased to 70.96% for the second group specimens (p=0.035). There were, however, no significant differences in biaxial flexural strength between the two groups using t-test.
Conclusions: Sintering Zirconia in the covered and uncovered crucibles showed different grain size, distribution, and CR. There was no significant difference in biaxial flexural strength.