الفهرس 
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Abstract
The repeated firing of ceramic restorations might be encountered on a daily basis in the process of fabrication of all ceramic restoration in the dental laboratories which in turn might have a determinant effect upon the final esthetic outcome of all ceramic restoration in terms of color and translucency changes.
Therefore, in our present study, the effect of multiple firing cycles with different firing temperatures on shade and translucency of the newly introduced obsidian material which is a lithium silicate based was investigated.
Forty-eight rectangular samples were cut using Isomet 4000 sawing machine providing two different thicknesses of 0.5mm and 1mm of sample size 24 for each thickness.
Furthermore, each 24 samples were divided into 3 subgroups according to the number of firing cycles where subgroup F1 was the control group for baseline reference. The other 2 subgroups were subjected to different firing cycles with different temperatures.
The translucency and color changes were assessed by the use of spectrophotometer against white and black background panels.
All data were collected, tabulated and statistically analyzed to detect any significant values among the tested groups.
The following results were obtained:
The results for translucency parameters revealed that:
1. For T0.5 group, F3 subgroup had the highest mean values of translucency parameter while the lowest mean value was recorded with F1 subgroup although results were statistically non-significant.
2. For T1 group, F1 subgroup had the highest mean values of translucency parameter while the lowest mean value was recorded with F5 subgroup although results were statistically non-significant.
3. T0.5 groups showed higher mean values of translucency parameter when compared to T1 groups regardless of the number of firing cycles which was statistically significant.
While the results for color change revealed that:
1. For T0.5 group, F3 subgroup had a higher mean values of color change while the F5 subgroup had the lowest mean values although results were statistically non-significant.
2. For T1 group, F5 subgroup had a higher mean values of color change while the F3 subgroup had the lowest mean values and the results were statistically significant.
3. T0.5 groups showed higher mean values of color change when compared to T1 groups regardless of the number of firing cycles although results were statistically non-significant.