A Novel Zirconia Composition for Speed Sintering with Enhanced Properties

Abstract

Despite being introduced into restorative dentistry nearly 30 y ago and having evolved into the most widely used ceramic restorative system, zirconia has only recently become available for chairside, same-day treatments, thanks to the development of high-speed sintering technology. However, recent studies have revealed that high-speed sintering not only severely compromises the translucency of dental zirconias (particularly in 3YSZ and 5YSZ) but also alters the translucency hierarchy among these compositions. Building on these critical findings, we hypothesized that a composition between 3YSZ and 4YSZ, such as 3.5YSZ, may be better suited for high-speed sintering protocols, offering both excellent strength and translucency. To test this hypothesis, 30 disc-shaped 3.5YSZ were uniaxially pressed, followed by cold-isostatic pressing and bisque firing. These presintered discs were then subjected to high-speed sintering using a commercial 18-min zirconia speed-fire protocol. Translucency parameters (TP and TP₀₀; n = 18), contrast ratio (CR; n = 18), and biaxial flexural strength (n = 18) tests were conducted, along with density (n = 10), microstructural (n = 3), and compositional (n = 3) characterizations. Our findings show that high-speed sintered 3.5YSZ exhibited superior TP and CR values (P < 0.0001) compared to existing YSZ counterparts, while maintaining the high-strength characteristic of 3YSZ (P = 0.7420). The clinical implications of this newly developed composition, as well as future directions for fabricating this material with improved translucency and strength for efficient chairside workflows, are discussed.

Keywords: 3.5Y-TZP; Weibull analysis; biaxial flexural strength; high-speed sintering; theory of reflection and refraction; translucency parameter.