Optical and Mechanical Properties of the Multi‐Transition Zones of a Translucent Zirconia

Abstract

ABSTRACT Objective To characterize the composition, flexure resistance, and optical properties of a multilayer translucent zirconia in relation to its multi‐transition zones. Materials and Methods A multilayer zirconia (5Y/4Y) and a conventional 3 mol% yttria partially stabilized zirconia (3Y) were investigated. Bar‐shaped specimens were obtained from the enamel and dentin layers, and the vertical cross‐section of 5Y/4Y ( N = 10). A four‐point flexural ( σ f ) test was performed using a universal testing machine (1.0 mm/min). Plate‐shaped specimens ( N = 6) were also produced from the enamel, transition 1, transition 2, and dentin layers. Translucency parameters (TP ab and TP 00 ) were determined using a dental spectrophotometer ( N = 6). X‐ray fluorescence and X‐ray diffraction techniques were used to analyze elemental ( N = 2) and phase compositions ( N = 2), respectively. Data were analyzed using analysis of variance (ANOVA) and Tukey's test ( α = 0.05). Results The yttrium content and σ f varied between layers of 5Y/4Y. 3Y had the highest σ f , followed by dentin. Enamel and cross‐section showed lower and statically similar σ f . 3Y and dentin groups had similar but statistically lower TP ab and TP 00 than the enamel. Conclusions Different layers of multilayered zirconia have distinct compositions, which affect their mechanical and optical properties. The weak enamel layer compromises the mechanical properties of cross‐sectional specimens. Clinical Significance The development of novel cubic‐containing multilayer zirconia ceramics to produce monolithic restorations brings new challenges to dental clinicians and laboratory technicians. The CAD/CAM design of multilayered 5Y/4Y restorations should consider the esthetic and mechanical requirements of each clinical case, as different properties are found in the different layers of these materials.

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