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

Objectives: Objective: To evaluate the fracture resistance of endodontically treated mandibular molars restored with the Endocrown method versus amalgam cores with various level of ferrule
Methods: Methods: 48 recently-extracted mandibular third molars were randomly divided into 4 groups (n=12) with the coronal tooth structure removed perpendicular to the root long axis at the facial-lingual height of contour with a water-cooled, slow-speed diamond saw. The pulp chamber was exposed using diamond 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 endocrowns with a 2mm pulp chamber extension. The other three groups were restored with a dispersed phase, high copper, amalgam cores (Permite, SDI) that were prepared for full all-ceramic crowns with 1mm, 2mm, and minimal ferrule (< 0.5mm). Completed preparation surface area was determined using a digital measuring microscope (Hirox). Scanned preparations (CEREC) were fitted with e.max CAD crowns and luted with RelyX Unicem after HF acid etching and silanation. All manufacturer recommendations were followed. Specimens were stored at 37C/98% humidity and tested to failure after 24 hours at a 45-degree angle to the long axis on a universal testing machine. Failure load was converted in MPa using the available bonding surface area with mean data analyzed with Kruskal-Wallis/Dunn’s (p=0.05).
Results: Results: Results are listed in the table.
Conclusions: Conclusions: Under this study’s conditions, mandibular molars restored with amalgam cores with minimal- and 1mm ferrule preparation design displayed greater resistance to failure stress compared to the other groups.