Tehran University of Medical Sciences Frontiers in Dentistry 2676-296X 19 0 2022 09 12 3892 3892 Armaghan Shahbazi Department of Prosthodontics, Faculty of Dentistry, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran Fariborz Vafaei Dental Implants Research Center, Department of Prosthodontics, School of Dentistry, Hamadan University of Medical Sciences, Hamadan, Iran. Amirarsalan Hooshyarfard Dental Materials Research Center, Tehran Medical Sciences, Islamic Azad University, Tehran, Iran AND Department of Periodontics, Faculty of Dentistry, Shahed University, Tehran, Iran Erfan Nosrati Doctor of Dental Surgery Masood Nazari Private Practice, Hamadan, Iran Maryam Farhadian Department of Biostatistics, School of Public Health and Research Center for Health Sciences, Hamadan University of Medical Sciences, Hamadan, Iran. 2020 12 18 2021 07 13 Objectives: Any change in the sintering process can directly affect the micro-structure and properties of zirconia. This study sought to assess the effect of sintering temperature on flexural strength of IPS e.max ZirCAD MO Ivoclar (EZI) and CopraSmile White Peaks Symphony (WPS) zirconia blocks. Materials and Methods: In this in vitro, experimental study, 30 EZI and 30 WPS zirconia blocks measuring 10 x 10 x 1 mm were milled and sintered at 1440, 1500 and 1530°C in three subgroups. The flexural strength of the specimens was measured by a testing machine with piston-on-3-ball method according to ISO2015. Data were analyzed using one-way ANOVA. Results: The mean flexural strength was 1.31±0.49, 1.09±0.24 and 1.29±0.48 MPa in 1440, 1500, and 1530°C subgroups of EZI, and 1.44±0.61, 1.18±0.35, and 1.33±0.54 MPa in 1440, 1500, and 1530°C subgroups of WPS zirconia, respectively. Two-way ANOVA revealed that the effects of zirconia type (P=0.484), temperature (P=0.258) and their interaction (P=0.957) on flexural strength were not significant. Conclusion: Increasing the sintering temperature from 1440°C to 1530°C did not increase the flexural strength of EZI or WPS zirconia.  https://fid.tums.ac.ir/index.php/fid/article/view/3892