The Effect of using Two Sintering Cycles on the Optical Properties of Gradient Multi-Layered Zirconia (In vitro Study)

Abstract

Objective: The study evaluates how thermocycling aging and variations in sintering parameters, using conventional and speed cycles, affect the optical properties of two types of multilayered zirconia compared to lithium disilicate. Materials and methods: Thirty-five disc-shaped samples of 12 mm diameter and 0.5 mm thickness were constructed using IPS e.max ZirCAD Prime (Ivoclar, Vivadent, USA) and Katana UTML (Kuraray Noritake Dental Inc), comparing them to lithium disilicate IPS e.max CAD (Ivoclar, Vivadent, USA). half using each sintering method. color and translucency were measured before and after themocycling performed for 5000 cycles to simulate 6 months in the oral environment using spectrophotometer. Results: significant differences among groups were found, with IPS e.max CAD having the highest translucency, followed by Katana, and IPS e.max Zircad Prime the lowest. Conventional cycles exhibited higher values than speed cycles pre- and post-aging. IPS e.max CAD's translucency decreased after aging, while both zirconia types showed increased translucency after aging. Katana had the highest color change, followed by IPS e.max ZirCAD Prime, and IPS e.max CAD the lowest, in both sintering cycles. Speed sintering induced more color change than conventional. Conclusion: conventional sintering yielded higher translucency compared to speed, and speed caused greater color change in Katana. Thermocycling aging increased translucency for Katana and IPS e.max ZirCAD Prime but decreased it for IPS e.max CAD.