Fracture Strength of CAD/CAM versus Contemporary Bis-Acryl Provisional Crowns

Introduction: Provisional restorations have an important role in prosthodontic treatment, designed to protect teeth until delivery of a definitive restoration. CAD/CAM milled and traditional chair-side provisional fabrication techniques are widely used in clinical practice. Despite the advantages of CAD/CAM, direct chairside fabrication of provisional restorations using bis-acryl material is still a common procedure due to convenience and low costs. The investigation of contemporary bis-acryl materials will aid the clinician in making educated decisions on which material to choose for provisional restorations. Objective: To compare the fracture strength and mode of fracture of CAD/CAM milled provisional crowns versus directly fabricated contemporary bis-acryl material under a laboratory environment. Methods: Bis-acryl based materials, Luxatemp Ultra (LT, DMG) and LuxaCrown (LC,DMG) were used to fabricate provisional crowns utilizing conventional direct technique. Polymethyl methacrylate Telio CAD (TC, Ivoclar Vivadent) and acrylate polymer Vita CAD-temp (VC, Vita) were milled from monolithic blocks with CAD/CAM technology. Crowns were cemented with temporary cement (TempBond NE, Kerr) onto 3D-printed photopolymer resin model dies (Formlabs, n=10/group). A universal testing machine (MTS 858 Mini Bionix II test system) applied a compression load at a crosshead speed of 1 mm/min to individual samples until failure. The average value at failure and the mode of fracture were recorded.