الفهرس 
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Abstract
Introduction: The restoration of endodontically treated teeth is a challenging dental procedure. Custom made post and core is indicated in cases of extensive coronal tooth destruction where additional retention is required. The adaptation of posts to root canals has been identified as the main factor associated with the failure threshold of restored teeth. Cast post and core restorations can be fabricated by means of an impression of the prepared canal using an elastic impression material or via a resin pattern technique. A new method of fabricating a custom made post and core is the use of CAD/CAM technology (computer-aided design/computer-aided manufacturing) to generate the post and core restoration from a ceramic block. The properties of the hybrid ceramic block make the material suitable for chairside CAD-CAM post-and-core fabrication.
Aim of the study: Is to evaluate the effect of two different intracanal impression techniques on the accuracy of fit of CAD/CAM hybrid ceramic post and core restorations.
Materials and method: Twenty single-rooted mandibular first premolars will be selected then endodontically treated and prepared to receive post and core restorations. The specimens will be randomly divided into two equal groups according to the intracanal impression technique that will be used: CAD/CAM generated post and core restorations for group I will be obtained by scanning the anatomy of the canal using autopolymerizing acrylic resin (Duralay) patterm on a plastic post. For group II polyvinyl siloxane impression of the post space will be scanned. Data from both groups will be processed using CAD-CAM software then the post and core restorations will be developed from milling of hybrid ceramic blocks and cemented using a self-adhesive resin cement. All of the 20 specimens will be then sectioned longitudinally and the post and core adaptation will be evaluated using the stereomicroscope. Data will be statistically analyzed using ANOVA test.
Keywords: Post and core, CAD/CAM, Accuracy, Hybrid ceramic.