title: Translucency of monolithic and core zirconia after hydrothermal aging.
abstract: Objective: To evaluate the hydrothermal aging effect on the translucency of partially stabilized tetragonal zirconia with yttria (Y-TZP) used as monolithic or fully milled zirconia and of core type.Methods: Twenty disc-shaped specimens (1 and 10 mm) for each type of monolithic and core Y-TZP materials were milled and sintered according to the manufacturer's instruction. The final specimens were divided into two groups according to the type of Y-TZP used. Translucency parameter (TP) was measured over white and black backgrounds with the diffuse reflectance method; X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to analyze the microstructure of both Y-TZP types before and after aging. Data for TP values was statistically analyzed using Student'st-test.Results: Monolithic Y-TZP showed the highest TP mean value (16.4 ± 0.316) before aging while core Y-TZP showed the lowest TP mean value (7.05 ± 0.261) after aging. There was a significant difference between the two Y-TZP types before and after hydrothermal aging. XRD analysis showed increases in monoclinic content in both Y-TZP surfaces after aging.Conclusion: Monolithic Y-TZP has a higher chance to low-temperature degradation than core type, which may significantly affect the esthetic appearance and translucency hence durability of translucent Y-TZP.
authors.affiliation: Department of Dental Biomaterial, Faculty of Dentistry, Mansura University , Mansoura , Egypt.
authors.forename: Salma M
authors.initials: SM
authors.lastname: Fathy
authors.affiliation: Department of Dental Biomaterial, Faculty of Dentistry, Mansura University , Mansoura , Egypt.
authors.forename: Abeer A
authors.initials: AA
authors.lastname: El-Fallal
authors.affiliation: Department of Dental Biomaterial, Faculty of Dentistry, Mansura University , Mansoura , Egypt.
authors.forename: Salwa A
authors.initials: SA
authors.lastname: El-Negoly
authors.affiliation: Department of Physics, Faculty of Science, Mansura University , Mansoura , Egypt.
authors.forename: Abu Baker
authors.initials: AB
authors.lastname: El Bedawy
keywords: Translucent zirconia; low-temperature degradation; microstructure