CAD/CAM Preparation Design Effects on Endodontically Treated and Restored Molars

Objective To evaluate the fracture resistance of adhesively-bonded, full coverage ceramic restorationsmanufactured by a CADCAM technique on endodontically treated molars restored with the endocrown method versus ceramic full coverage based on amalgam cores with different ferrule design. Methods 84 recently-extracted mandibular third molars were randomly divided int o 7 groups nl2 with the coronal tooth structure removed perpendicular to the root long axis at the facial-lingua l height of contour with a water-cooled, slow-speed diamond saw. The pulp chamber was exposed usingdiamond burs in a high speed handpiece, pulpal remnants removed, and canals instrumented using endodontic hand instruments. Specimens were embedded in autopolymerizing denture base resin. One group was restored with a lithium disilicate endocrown with a two millimeter pulp chamber extension.The other three groups were restored with an amalgam core using a dispersed phase, high copper amalgam that were prepared for a full coverage lithium disilicate crown with preparation designs including one and two millimeters of ferrule, plus one group with an external marginal finish line approximating the intracoronal dentin amalgam interface minimal ferrule.