الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
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Abstract
Recently, the importance of cosmetic dentistry increased rapidly because of raised patient awareness and requirements. To reproduce a matching tooth color and respond to the expectations of patients, even in high strength restorations, accurate evaluation of the natural tooth color and studying the parameters influencing the shade of the final prosthesis is mandatory.
This study was performed on high strength nano-crystalline translucent zirconia to evaluate the effect of immersion time in coloring liquid and final sintering holding temperature on translucency and shade reproduction of monolithic zirconia restorations.
Translucent zirconia blocks (inCoris TZI 40/19) were sliced to produce 45 translucent zirconia slices. Each slice was milled and finished to produce rectangular specimens of dimensions 15.5 x 19 mm . The forty five slices were divided into 3 main groups, 15 slices each, according to their coloring immersion times; GP A (3 minutes) ,GP B (5 minutes) and GP C (7 minutes). All the specimens were dipped in an A3 inCoris TZI coloring liquid. Each main group was further subdivided into 3 subgroups , 5 slices each, according to their final sintering temperatures; sub groups 1,2 and 3 , at temperatures 1400 ,1500 ,1600 respectively.
After final sintering of all the slices, a digital spectrophotometer (Vita EasyShade Compact) was used to measure L*, a* and b* coordinates values according to the CIELAB color system against white background for shade measuring and against both white and black backgrounds for translucency measurement. The values were recorded, tabulated and ΔL, Δa, Δb, ΔE and translucency parameter (TP) values for each specimen were calculated against those recorded from L* , a* and b* coordinates values from a Vita classic A3 shade tab. The results were statistically analysed. A scanning electron micrograph of a random sample from each of the sintering groups was recorded and interpreted.
Results showed that the color saturation (Δa, Δb, ΔE) were affected by the dipping time (increased with increased time) and the sintering temperature. However, as for the translucency parameter it was mainly affected by the final sintering holding temperature (transmittance increased with higher temperatures). Also, it is to be noted that the effect of the increased color saturation generally lead to a less value (ΔL) and had a slight effect on translucency as increased pigments saturation decreased light transmittance.