Ceram x universal

The cavities were restored in one increment with a nano-hybrid composite (Ceram X Universal, Dentsply Sirona, Konstanz, Germany) and light cured for 20 s. Excess of composite was removed with surgical scalpel blades (No. 12D, Gebr. Martin, Tuttlingen, Germany), and the restorations were polished under a microscope at 25× magnification (Stemi 2000, Zeiss, Oberkochen, Germany) using silicon instruments (Brownie Mini-Points and Greenie Mini-Points, Shofu Dental Corporation, San Marcos, CA, USA) and polishing brushes (Occlubrush, Kerr, Orange, CA, USA).
The specimens were then thermocycled by dipping them 5000 times alternately in water baths with temperatures of 5 and 55 °C, with a dwell time of 20 s in each bath and a transfer time of 10 s [14 (link),17 (link)].

Forty CPR compules were used, representing four different commercial products. Three products are marketed as a universal CPR: Herculite XRV Ultra (LOT # 5469627, Kerr, Bioggio, Switzerland), Ceram.X Universal (LOT # 1702000550, Dentsply Sirona, York, PA, USA), Tetric Evo Ceram (LOT# V47223, Ivoclar Vivadent, Schaan, Liechtenstein). One product is marketed as a flowable bulk-fill composite, SDR (LOT# 1701000793, Dentsply Sirona, York, PA, USA). All products were purchased from a commercial dental supplier in Norway (Dental Spar AS, Drammen, Norway).