الفهرس 
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Abstract
A variety of all-ceramic systems is commercially available and can offer a new esthetic dimension, particularly in anterior teeth. Among these materials are lithium disilicate ceramics and zirconia reinforced lithium silicates. These two categories are known for the strength and superior esthetics making them of great use in the cosmetic dentistry field.
Adequate polymerization is crucial for determining the life of resin bonded ceramic restorations. Incomplete polymerization of the cement may lead to color instability, toxicity from residual monomer, decreased bond strength, and post-operative sensitivity, leading to increased risk of microleakage, food impaction and caries.
Since most of these cements are photo polymerized, adequate light-curing is important to ensure long term success of restorations.
In view of these considerations, there’s a hypothesis that thickness of a ceramic will interfere with the polymerization of the cements to such a degree that it will change the water sorption and solubility of this material; similarly, the type of the cement might also influence the outcome. Thus, the objective of this study is to evaluate the water sorption of light-cured cements using ceramic slides of different thicknesses and different ceramic materials.
Sixty ceramic slices were machined from their respective blocks by using an isomat to uniform standard thicknesses of (0.4 mm and 1.0 mm). Three materials were used, IPS emax CAD, VITA Suprinity and Celta Duo. A digital caliper was used to check the thicknesses. Two Teflon molds were be fabricated according to the thicknesses ceramic disks that were seated on the inner stopper of the mold to ensure a standard thickness of resin cement samples.
Light curing was done using high intensity LED light curing unit for 20 seconds where the tip was in direct contact with the ceramic disc.
Cement specimens were then separated from the ceramic discs, placed in a dessicator containing fresh silica gel and placed in an incubator, repeatedly weighed after 24h intervals until a constant mass (m1) was obtained (i.e., variation was less than 0.2mg in any 24h period) using an analytical balance of accuracy 0.001 g, length width and thickness measured using a digital caliber. Volume (V) was calculated in cubic millimeters (mm3).
Cement specimens where then placed in glass sealed containers containing 10 ml distilled water, placed in an incubator and repeatedly weighed until a constant mass was obtained (m2).
The final step was placing specimens again in a dessicator containing fresh silica gel and placed in an incubator, repeatedly weight after 24h intervals until a constant mass (m3) was obtained
The equation below was used to measure water sorption.
WS=(m2-m3)/V;
Results of the study showed that the two thicknesses had no effect on the water sorption of the underlying cement while different materials affected it. Celtra Duo and Vita Suprinity caused significantly less water sorption than IPS emax CAD with no significant difference between them.