الفهرس 
Introduction and aim of the workOnly 14 pages are availabe for public view
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Abstract
The effects of ageing on both pre-shaded and liquid-shaded zirconia crowns were examined in this study. The in-vitro portion of the research focused on the effects of staining liquids on the colour, translucency, and flexural strength of zirconia ceramic before and after ageing using acetic acid 4% as the ageing medium.
The in-vitro portion, A.
Sixty disc-shaped samples were made from zirconia ceramic (Zolid HT). Shading method was used to split the samples in half (n=30). The first group (n=30) was made from pre-shaded zirconia and split into two subgroups (A2 shaded, n=15) and A4 shaded (n=15), with each of these further split into two classes: the first class (n=5) was used to evaluate the colour and translucency of the blocks before and after ageing, and the second class (n=10) was used to evaluate the flexural strength of the blocks before and after ageing. The second set (n=30) was made from clear zirconia and divided into two subsets (n=15 each) based on the shade of colouring liquid used: the first set was tinted with A2 shade, and the second set was tinted with A4. Finally, each set was split into two classes: the first set (n=5) was tested for colour and translucency before and after ageing, and the second set (n=10) was tested for flexural strength.
In-vivo part:
In this research, nine participants were chosen to have their six front upper teeth trimmed down. Forty-five patients were fitted with zirconia crowns, and they were split into two groups based on the colouring method used to create the crowns. In this case, crowns made of pre-shaded zirconia were placed on the upper right front teeth, whereas crowns made of liquid-shaded zirconia were placed on the upper left front teeth. After a year, the colour parameters were evaluated.
The following are the results from the data collection, tabulation, and statistical analysis:
(1) The amount of colour change over time was significantly affected by the shade of zirconia ceramic, with A2 shade having a change in E that was within the clinically acceptable range.
Zirconia’s E deviates from its initial value over time depending on the process used to colour it; this effect is particularly pronounced for opaque colours like A4, however it is seen with all colouring methods.
When comparing the same colour before and after ageing and also when comparing the pre-shaded and the liquid shaded samples of the same hue, there was no significant influence on translucency.
In whatever colouring method and at any age, the A2 shade of zirconia ceramic was more transparent than the A4 shade.
The flexural strength is unaffected by the colour of the zirconia ceramic used (5 points).
(6) After age, the flexural strength of zirconia ceramic increases with the pre-shaded samples and decreases with the liquid shaded samples, independent of colour.
The flexural strength of zirconia ceramic is influenced by many factors, including but not limited to: (7) the passage of time, the colouring process used, and their interaction.
Clinical Recommendations: (8) Good oral hygiene practises are crucial to the long-term aesthetic effectiveness of the restoration (In-vivo).
As its hue changes very little over time, pre-shaded zirconia ceramic comes highly recommended.
Second, its flexural strength doesn’t decrease with age.
The translucency of a material may be enhanced by careful attention to its hue.
c. Pre-shaded or liquid-shaded zirconia crowns may be utilised in vivo, since their colour retention after ageing is within the clinically acceptable range (In-vivo)
Choosing the right patients is crucial to the long-term effectiveness of the restoration (In-vivo).