Effect of Simulated Mastication on Structural Stability of Prosthetic Zirconia Material after Thermocycling Aging

Abstract

Recent trends to improve the aesthetic properties—tooth-like color and translucency—of ceramic dental crowns have led to the development of yttria-stabilized zirconia (Y-TZP) materials with higher stabilizer content. These 5Y-TZP materials contain more cubic or t’ phase, which boosts translucency. The tradeoff as a consequence of a less transformable tetragonal phase is a significant reduction of strength and toughness compared to the standard 3Y-TZP composition. This study aims at determining the durability of such 5Y-TZP crowns under lab conditions simulating the conditions in the oral cavity during mastication and consumption of different nutrients. The test included up to 10,000 thermal cycles from 5 °C to 55 °C “from ice cream to coffee” and a chewing simulation representing 5 years of use applying typical loads. The investigation of the stress-affected zone at the surface indicates only a very moderate phase transformation from tetragonal to monoclinic after different varieties of testing cycles. The surface showed no indication of crack formation after testing. It can, therefore, be assumed that over the simulated period, dental crowns of 5Y-TZP are not prone to fatigue failure.

Comparison of the Surface Roughness of CAD/CAM Metal-Free Materials Used for Complete-Arch Implant-Supported Prostheses: An In Vitro Study

“…In contrast, both zirconia groups (ZF-ZM) showed intra-group differences between initial and post-TMCL values. This can be explained by the zirconia's susceptibility to LTD, which involves a slow transformation from the tetragonal (t) to monoclinic (m) phase, induced by thermal or mechanical stress, and exacerbated in the presence of water, causing a surface deterioration [38]. The presence of Al 2 O 3 stabilizes the tetragonal phase and improves hydrothermal ageing resistance; therefore, when the alumina content decreases (≤0.05 wt.%), zirconia is more translucent but more susceptible to LTD [39].…”

Effect of Acid Surface Treatments on the Shear Bond Strength of Metal Bracket to Zirconia Ceramics

“…Aesthetic concerns among dental patients have shifted the paradigm from metalbased restorations towards all-ceramic restorations. Zirconia is commonly recognized for its superior mechanical qualities [1,2], biocompatibility, aesthetics, and easy digital fabrication through computer-aided design/computer-aided manufacturing (CAD/CAM) technology [3][4][5]. This suggests the greater probability of a dentist encountering zirconia restorations in the oral cavity during orthodontic treatment.…”