Abstract
Objective: Despite the higher translucency of nano-crystalline 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 (?E) 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). (?E) 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 ?E and TP. Glass graded group showed the highest ?E 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.KeywordsAging; Ceramic restoration; Color; Translucent.
Highlights
During the last few decades, the demand for metal-free restorations, being conditioned by both social pressures and interests of dental profession has increased dramatically and a climate of non-acceptance of metal alloys in the oral cavity prevailed [1]
Results showed that different surface treatment methods applied had significant effect (P
When color change (∆E) and translucency parameter were calculated, the glass graded group showed the highest amount of color change and the least (TP) value among both un-aged and aged sub-groups (Table 1)
Summary
During the last few decades, the demand for metal-free restorations, being conditioned by both social pressures and interests of dental profession has increased dramatically and a climate of non-acceptance of metal alloys in the oral cavity prevailed [1]. This would in return affect the behavior of the incident light from underneath the inherently translucent veneering porcelain and have an effect on the color and translucency of the whole bilayered structure Another major drawback we face when using Y-TZP is low temperature degradation (LTD) which is the spontaneous tertragonal to monoclinic (t-m) transformation occurring over time at low temperature and humid atmosphere. That In-vitro study was carried out to evaluate color change and translucency parameter of the translucent nano-crystalline bilayered zirconia restorations after different treatments of the zirconia surface before and after accelerated autoclave aging. All veneered translucent nanocrystalline zirconia discs were finished and polished using a fine polishing disc of porcelain polishing kit (Microdont, São Paulo, Brazil) in a straight handpiece and glazed with VITA AKZENT glaze and fired Both color change and translucency parameter were measured using VITA Easyshade Compact Two-tailed tests were assumed through- out the analysis for all statistical tests
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