Key Physico-Mechanical Properties of Zirconia-reinforced Lithium Silicate Glass-ceramics

Abstract

Since lithium-silicate glass-ceramics (LSCs) were introduced to dentistry, their formulations have been modified significantly to meet the multifaceted aesthetic and mechanical requirements of dental restorations. Therefore, the focus of this thesis was to investigate various spectrophotometric, topographic, and mechanical aspects of novel zirconia-reinforced lithium silicate glass-ceramics (ZLSs) as a function of different intaglio and external surface treatments. The first part of this research applied intaglio treatments of acid etching and/or acid neutralising combinations to CAD/CAM LSCs (e.max CAD, VITA Suprinity, Celtra Duo and CEREC Tessera). Ceramic-related properties (light transmission, absorbance, roughness, wettability, and flexural strength) and light curing unit-related properties (transmitted irradiance, power, and radiant exposure) were assessed. Post-etching neutralisation did not detrimentally alter the micro-retentive intaglio features, and, neutralised LSCs demonstrated relatively adequate aesthetic and mechanical stability. The second part of this thesis assessed external treatments of varying firing/glazing protocols applied to fully crystallised CAD/CAM LSCs (Initial LiSi Block, Celtra Duo and CEREC Tessera). Thereafter, light transmission, roughness, gloss, hardness, flexural strength and crystalline phases were evaluated. Overall, single and duplicate firing treatments yielded favourable strength results, whereas glazing led to the strength deterioration of fully crystallised LSCs. The third part analysed the stain susceptibility and topography of pressable and machinable ZLSs (VITA AMBRIA, Celtra Press, VITA Suprinity, and Celtra Duo). Stain susceptibility of ZLSs concluded to be dependent on their fabrication methods as well as translucency and thickness levels.