Samueli School of Engineering

With approximately 1 in 20 individuals experiencing tooth fractures annually, there is a pressing demand for dental restorations. However, commercially available dental restoration options force consumers to compromise between aesthetics and mechanical properties. Highly esthetic cubic yttria-stabilized zirconia (YSZ) deviates from the popularity of standard tetragonal 3 mol% YSZ bioceramic due to its insufficient mechanical properties for practical dental applications. Yet, a tantalum functional gradient coating (FGC) applied to cubic YSZ has been demonstrated to enhance mechanical properties beyond even that of undoped 3 mol% YSZ, while maintaining adequate transparency values—corroborated by mechanical and optical testing. A combination of SEM, EDS, XRD, and Raman spectroscopy were employed to elucidate the mechanisms behind the change in mechanical and optical properties upon varying tantalum dopant concentrations. Tantalum defects within the YSZ lattice decrease cubic phase stability, locally inducing monoclinic phase transformations around cracks, subsequently arresting their propagation. Although the monoclinic crystal structure diminishes optical isotropy, the negative impact on transparency is deemed negligible for dental restoration applications. Advisors: Drs. Chriss Hoo, Shen Dillon, David Kisailus, jae-Won Kim