الفهرس 
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Abstract
This study was designed to evaluate the effect of two different materials and two preparation designs on the marginal adaptation and microleakage of CAD/CAM machined laminate veneers.
Twenty natural central incisors were selected to receive a standard veneer preparation with difference only proximally. Ten were constructed to receive nanocceramic composite material (Lava Ultimate 3M) and the other ten received the conventional leucite reinforced ceramic (IPS Empress CAD). Within each group five were prepared with a standard preparation where the preparation was confined to the labial surface with no proximal extension. The other five had their proximal contact sliced so that veneer preparation ended just lingual to the contact.
Twenty CAD/CAM milled veneers were constructed to fit on the corresponding scanned teeth for each proximal preparation, using inLab 3D software (V3.8). Using a stereomicroscope with a digital camera, the vertical marginal gaps were measured for the four different margins of each veneer. The internal surfaces of the veneers were sandblasted, and the internal surfaces of the leucite reinfocred veneers were etched using hydrofluoric acid gel and then were silanized by a primer before application of resin cement. However, no etching was done for the nanoceramic composite group.
The veneers were seated, during cementation, utilizing static finger pressure. The mean vertical gap (in microns) for each specimen was then calculated and saved in an Excel sheet for statistical analysis. The teeth with the cemented laminates were then placed in 2% methylene blue dye solution for 24 hours in an incubator at 370 C. They were then embedded in clear acrylic resin and sectioned labiopalatally into two equal halves. Microleakage was evaluated using scores at the cervical and incisal regions.
One-Way ANOVA test was used to examine effects of the different materials and of the different preparations on the marginal adaptation. The Independent-Samples T Test was used to examine the effect of material on marginal adaptation and effect of preparation on marginal adaptation independantly. It was also used to examine the effect of material on microleakage.
The results showed significantly better marginal gap values for the Lava Ultimate group than the IPS Empress CAD group, with no significant effect of preparation design on the marginal adaptation. As for microleakage, there were significant differences between the two materials with higher microleakage in the Lava Ultimate group.