الفهرس 
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Abstract
Degree of conversion of resin cements used in bonding lithium silicate ceramic restorations has a great effect on long-term success of these restorations.
The present study showed the effect of ceramic thickness and its shade on the degree of conversion of the light cured resin cement when three different lithium silicate ceramics were used.
Materials and methods: 84 ceramic samples were prepared from three types of ceramics, Emax CAD, Celtra Duo CAD and Vita suprinity CAD (n=28). They were further divided into two subgroups according to thicknesses into sub group thickness 0.5mm and sub group thickness 1mm (n=14). They were then divided according to resin cement shades A2 and translucent (n=7). Teflon moulds were fabricated with specific dimensions, where the ceramic slice was placed followed by light cured resin cement Bisco choice 2 veneer and a glass slab with finger pressure applied. Curing with Bluephase Ascent ® PX LED light cure unit for 20 seconds took place, where the tip was in direct contact with the ceramic sample. Cement film was then separated from the ceramic slice and subjected to analysis by Fourier Transform Infrared Spectroscope. Uncured cement samples were also subjected to analysis. Both values were used in the equation below to obtain the degree of conversion.
For composites having internal standard, the percentage of unreacted aliphatic C=C bonds remaining throughout the polymerization reaction is obtained by the equation:
where Abs can be the height or the area of absorption band.
DC is determined by subtracting the residual percentage of aliphatic C=C from 100% (DC%=100-(%C=C)
Results showed higher degrees of conversion with the translucent resin shade than the A2 shade. Celtra DUO ceramic showed higher degree of conversion of the resin cement that of Emax and Vita suprinity while there was no significant difference in degree of conversion of the resin cement between Emax and suprinity. There was a significant effect on the degree of conversion with different thicknesses of the ceramic materials.