RESUMEN
PURPOSE: Speed sintering was introduced to fabricate time-efficient chairside restorations, however, its influence on the microstructure and optical properties of zirconia is still unclear. This study investigated the influence of speed sintering on the microstructure and optical properties of ultra-translucent multi-layered cubic zirconia. MATERIALS AND METHODS: Ultra-translucent cubic zirconia (Katana™ UTML; Kuraray Noritake Dental Inc., Aichi, Japan) was cut into a total of 80 specimens, twenty within each layer of the blank. The specimens were divided into 2 groups: speed and conventional sintering. The translucency parameter, opalescence, chromaticity, and color difference were recorded using a spectrophotometer. Scanning electron microscope images were used for crystallographic analysis. One-way ANOVA and Tukey's post-hoc test (p < 0.05) were used for data analysis. RESULTS: Speed sintering significantly reduced the translucency and opalescence compared to conventional sintering excluding the opalescence of the dentin layer. Chromaticity significantly decreased with speed sintering in less chromatic layers and significantly increased in more chromatic layers. Mean color change ranged between 0.65 and 1.25 across different layers. Mean crystal size decreased with speed sintering. CONCLUSIONS: With speed sintering, translucency, and opalescence decrease while chromaticity increases in the more chromatic layers. Additionally, no clinically perceptible color change was found compared to conventional sintering.
RESUMEN
Objective: Despite the higher translucency of nanocrystalline Y-TZP than the conventional Y-TZP, it couldn't be used in the anterior region of the mouth in its fully anatomical form without veneering for better esthetics. This study evaluated the color change (ΔE) and translucency parameter (TP) of the bilayered nano-crystalline zirconia restorations after different treatments of the zirconia surface before and after accelerated aging. Material and Methods: Forty samples of inCoris TZI were cut in the form of discs 15 mm (diameter) and 1mm (thickness) so that after sintering each disc dimensions' would be 12 mm (diameter) and 0.8 mm (thickness). All discs were colored by dipping in aqueous zirconia coloring solution of shade A2, then divided into four groups according to the type of surface treatment received before sintering; being tribochemical silica coating, zirconia powder deposition, glass grading, and a control untreated group. After sintering, all discs were veneered with a layer of porcelain 0.7 mm (thickness) and 12 mm (diameter). (ΔE) and TP were measured using VITA Easyshade Compact spectrophotometer before and after accelerated autoclave aging. Results: Different surface treatments applied had significant effect (P<0.05) over ΔE and TP. Glass graded group showed the highest ΔE value and the least TP value among both un-aged and aged sub-groups. Conclusion: Different surface treatments applied affected the color and translucency negatively where the control untreated group showed the highest TP and the least color deviation from the A2 color parameters. On the other hand, accelerated autoclave aging had no effect over translucency or color. (AU)
Objetivo: Apesar da maior translucidez da Y-TZP nanocristalina em relação à Y-TZP convencional, ela não pode ser usada na região anterior da boca em sua forma totalmente anatômica, sem o recobrimento cerâmico para uma melhor estética. Este estudo avaliou a mudança de cor (ΔE)eoparâmetrodetranslucidez(PT)das restauraçõesde zircônia nano-cristalina em duas camadas após diferentes tratamentos de superfície, antes e após o envelhecimento. Material e Métodos: Quarenta amostras de inCoris TZI foram cortadas na forma de discos de 15 mm (diâmetro) e 1 mm (espessura) para que, após sinterização, cada diâmetro dos discos fosse de 12 mm (diâmetro) e 0,8 mm (espessura). Todos os discos foram corados por imersão em solução aquosa de zircônia corante da sombra A2, divididos em quatro grupos de acordo com o tipo de tratamento de superfície recebido antes da sinterização; sendo revestimento de sílica químico-química, deposição de pó de zircônia, jateamento de vidro e um grupo de controle sem tratamento. Após a sinterização, todos os discos foram revestidos com uma camada de porcelana de 0,7 mm (espessura) e 12 mm (diâmetro). ΔE e TP foram medidos usando o espectrofotômetro VITA Easyshade Compact antes e depois do envelhecimento em autoclave. Resultados: Diferentes tratamentos de superfície aplicados tiveram efeito significativo (P <0,05) sobre ΔE o e maior TP. valor O grupo com de ∆E e o menor jateamento de vidro valor de TP apresentou entre os subgrupos não envelhecidos e envelhecidos. Conclusão: Diferentes tratamentos de superfície aplicados afetaram negativamente a cor e a translucidez, onde o grupo controle sem tratamento apresentou o maior TP e o menor desvio de cor dos parâmetros de coloração A2. Por outro lado, o envelhecimento acelerado da autoclave não teve efeito sobre a translucidez ou a cor. (AU)