الفهرس 
aim of the studyOnly 14 pages are availabe for public view
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Abstract
This in-vitro study was undertaken to evaluate the color stability and sorption oftwo types of resin cements and their effect on the color change of ceramic laminate veneers (IPS E.max CAD) havingtwo differentthicknesses (0.4 and 0.6mm thicknesses). For sorption and solubility tests, a total of 24 disc-shaped resin cement specimens (12 disks from each type of cement; NX3 LC and NX3 DC) were prepared by a specially prepared teflon mold. Out of 12 specimens/type of material, 6 discs were immersed in distilled water and the other 6 discs were immersed in coffee solution for 7 days at 37 ᵒC. Sorption and solubility micrograms/cubic millimeter (µg/mm3) for 1 week of storage were calculated.For the color change test of resin cements, disc-shaped resin cement specimens previously used in the sorption and solubility tests were also used forthe color change test. The color of specimens was measured, using a spectrophotometer (Vita Easyshade) before immersion in the storage solution and after a 7, 14 days immersion period in two different solutions, namely water and coffee. For color change of the cemented laminate veneers test, ceramic blocks (IPS E.max CAD) were cut into 48 disk-shaped laminate veneer (18mm x 16mm) using a microsaw, 24 of these samples were cut into .4mm thickness and the remaining 24 samples were cut into .6mm thickness. Afterward all samples were fired at 850 ᵒC to complete the crystallization process of (IPS E.max CAD). Afterwards, the samples’ssurfaces were glazed (E.max glaze, IvoclarVivadent) to obtain a smooth surface. A white-colored, durable and color stable Delrin material (acetalpolyoxymethylene) was chosen as a background material. Etching with HF 5% (Vita ceramic etch) was performed to the inner surface of ceramic veneer for 20 s, to be properly rinsed with water and dried. Afterwards, a silane-coupling agent (Ultradent) was applied to the etched specimens. During sample preparation, background disks were first inserted into the teflon molds, and the Optibond Solo Plus bonding agent was applied to the background material, which was cured for 20 s using a light-emitting diode (LED) light-curing unit (Elipar S10, 3M ESPE Elipar 1,200 mW/cm2). The resin cements were either directly applied from the syringe (LC) or they were mixed on a separate mixing pad (DC) and applied into the mold over a background Delrin disk. Afterwards, the ceramic veneer was inserted into the mold above the resin cement, to be covered with a glass slab. A load of .75 kg was applied for 30 s on the top surface of the glass slab to obtain 0.1mm even spread of cement thickness. All samples were cured. Afterwards, the samples were removed by dismantling the mold.Specimens were immersed in coffee and in water solutions for a period of 7, 14 days. Color evaluation was performed using a spectrophotometer (Vita Easyshade), and measurements were performed before immersion in the solutions, and after 7 and 14 days storage period. The color difference (ΔE) was obtained by calculating the color difference within each specimen before and after immersion in the solution.The results of sorption and solubility tests revealed greater sorption and solubility values for dual cured resin cement specimens compared to those of light cured types.The results of the color change test of resin cements revealed higher ΔE values for dual cured resin specimens, compared to those of light cured types.The results of the color change test of the cemented laminate veneers revealed higher mean ΔE values for ceramic veneers cemented with adual-cured resin cement compared to those cemented with light cured type. Also, the mean ΔE values of the cemented ceramic laminate veneer of a .4mm thickness was higher compared to those of the higherceramic thickness of .6mm