RESUMO
Dental zirconias have been broadly utilized in dentistry due to their high mechanical properties and biocompatibility. Although initially introduced in dentistry as an infrastructure material, the high rate of technical complications related to veneered porcelain has led to significant efforts to improve the optical properties of dental zirconias, allowing for its monolithic indication. Modifications in the composition, processing methods/parameters, and the increase in the yttrium content and cubic phase have been presented as viable options to improve zirconias' translucency. However, concerns regarding the hydrothermal stability of partially stabilized zirconia and the trade-off observed between optical and mechanical properties resulting from the increased cubic content remain issues of concern. While the significant developments in polycrystalline ceramics have led to a wide diversity of zirconia materials with different compositions, properties, and clinical indications, the implementation of strong, esthetic, and sufficiently stable materials for long-span fixed dental prostheses has not been completely achieved. Alternatives, including advanced polycrystalline composites, functionally graded structures, and nanosized zirconia, have been proposed as promising pathways to obtain high-strength, hydrothermally stable biomaterials. Considering the evolution of zirconia ceramics in dentistry, this manuscript aims to present a critical perspective as well as an update to previous classifications of dental restorative ceramics, focusing on polycrystalline ceramics, their properties, indications, and performance.
RESUMO
Monoclinic bismuth oxide (α-Bi2 O3 ) has attractive optical properties and, therefore, its photoluminescence (PL) behavior has been increasingly explored. Besides this fact, the influence of synthesis methods on PL properties of α-Bi2 O3 still requires research. This paper describes the influence of precipitation (PPT) and microwave-assisted hydrothermal (MAH) methods on PL properties of acicular α-Bi2 O3 microcrystals. The synthesis method promoted structural modifications on α-Bi2 O3 , in particular PPT increased the density of oxygen vacancies significantly. As a result, the PL properties of samples were different depending on the method of synthesis. PPT samples presented their maximum PL emission at 1.91 eV (red), while MAH samples had their maximum at 2.61 eV (blue). These results indicate the possibility of controlling PL properties of α-Bi2 O3 by simply choosing the adequate synthesis method.