Fracture Resistance of Ceramic Copings Fabricated from Zirconia and Zirconia-Reinforced Lithium Silicate Glass Ceramic

Abstract Background and Aim: In recent years, a variety of CAD/CAM materials have been developed to meet the aesthetic needs of prosthetic restorations. One of the major problems with all-ceramic restorations is their potential for fracture under occlusal and lateral forces. This in vitro study aimed to compare the fracture resistance) FR (of ceramic copings fabricated from zirconia and zirconia-reinforced lithium silicate (ZLS) ceramics. Materials and Methods: Sixteen identical dies were fabricated from clear epoxy resin, and randomly assigned to two groups (n=8) and coded. The dies were individually scanned by Ceramill scanner, and the copings were fabricated in two groups of Ceramill Zi zirconia and Vita Suprinity ZLS with 0.8 mm equal thickness by Ceramill Motion 2 (Amann Girrbach, Austria) milling machine, and were subsequently sintered. Each restoration was cemented on its respective die using GC Gold Label glass ionomer cement. All specimens were stored in saline at room temperature for 24 hours. They were then mounted in acrylic resin, and subjected to compressive force with 0.5 mm/min crosshead speed applied to the center of their occlusal surface longitudinally in a universal testing machine until fracture. Data were analyzed using T-test (α =0.05). Results: The force leading to fracture in zirconia group was measured as 749.7 N and in Vita Suprinity group amounted to 234.5N. Thus, the force amounts leading to fracture in sample groups displayed significant differences (p value < 0.001). Conclusion: Long-term resistance in using 0.8 mm thick copings of Vita Suprinity, cemented with glass ionomer, for clinical applications, is not assured. However, with regards to the most important advantages of ZLS, high esthetic and translucency, to Zirconia, more studies are required to prove clinical application of ZLS with thickness more than 0.8 mm by stronger adhesive bonding systems.