IADR Abstract Archives
Sintering Protocols Effects on Microstructure and Mechanical Properties of Recycled-Zirconia
Objectives: To assess the influence of the sintering heating rate on the microstructure and mechanical properties of recycled zirconia, relative to a commercially available 2nd-generation 3Y-TZP (Zpex, Tosoh) control.
Methods: Zirconia powder was collected from the vacuum cleaner system of milling equipments used exclusively for machining 3Y-TZP. The ceramic powder was then calcined at 900°C and sieved (200 mesh). Sixty discs of recycled 3Y-TZP, with 12 mm of diameter and 1 mm thickness, were obtained by uniaxial pressing. The samples were divided into groups for sintering at 1550°C for 2h, with different heating rates: 3°C/min and 10°C/min (n = 30). Samples of the control group were also obtained through uniaxial pressing and were sintered at 1550°C with a heating rate of 4°C/min. Microstructural and crystalline evaluations were performed using scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). Biaxial flexural strength test was performed using a piston-on-3-ball fixture following ISO 6872:2016. Weibull statistics were used to determine the characteristic strength and Weibull modulus of tested materials.
Results: SEM imaging demonstrated a greater grain size in the recycled zirconia sintered with the lower heating rate compared to higher heating rate. XRD analysis revealed a predominant tetragonal zirconia phase with no evidence of monoclinic peaks for all groups. The higher heating rate promoted a similar characteristic strength for the recycled zirconia [840 (CI 802-880) MPa] compared to the control group [840 (780-906) MPa], while the lower heating rate yielded a lower value [704 (CI 661-750) MPa]. No significant difference was observed between the groups in Weibull modulus (3.9 – 11.1).
Conclusions: The higher heating rate improved the mechanical properties of recycled zirconia. Recycled 3Y-TZP sintered with the higher heating rate exhibited comparable mechanical properties as the commercially available control. These findings support potential application of the experimental material for restorative dentistry.
Methods: Zirconia powder was collected from the vacuum cleaner system of milling equipments used exclusively for machining 3Y-TZP. The ceramic powder was then calcined at 900°C and sieved (200 mesh). Sixty discs of recycled 3Y-TZP, with 12 mm of diameter and 1 mm thickness, were obtained by uniaxial pressing. The samples were divided into groups for sintering at 1550°C for 2h, with different heating rates: 3°C/min and 10°C/min (n = 30). Samples of the control group were also obtained through uniaxial pressing and were sintered at 1550°C with a heating rate of 4°C/min. Microstructural and crystalline evaluations were performed using scanning electron microscopy (SEM) and X-Ray Diffraction (XRD). Biaxial flexural strength test was performed using a piston-on-3-ball fixture following ISO 6872:2016. Weibull statistics were used to determine the characteristic strength and Weibull modulus of tested materials.
Results: SEM imaging demonstrated a greater grain size in the recycled zirconia sintered with the lower heating rate compared to higher heating rate. XRD analysis revealed a predominant tetragonal zirconia phase with no evidence of monoclinic peaks for all groups. The higher heating rate promoted a similar characteristic strength for the recycled zirconia [840 (CI 802-880) MPa] compared to the control group [840 (780-906) MPa], while the lower heating rate yielded a lower value [704 (CI 661-750) MPa]. No significant difference was observed between the groups in Weibull modulus (3.9 – 11.1).
Conclusions: The higher heating rate improved the mechanical properties of recycled zirconia. Recycled 3Y-TZP sintered with the higher heating rate exhibited comparable mechanical properties as the commercially available control. These findings support potential application of the experimental material for restorative dentistry.