Tetric evoceram

All the specimen surfaces were covered by an adhesive tape of 100 μm thickness with a hole of a 3 mm in diameter, located at the center of each specimen. For each adhesive, 10 specimens were randomly selected and subjected to the priming treatments according to the manufacturers’ information. The adhesives were light-cured for 15 s with a LED curing unit (Radii Plus, SDI, Bainswater, Victoria, Australia, 1.5 W/cm² intensity at standard high intensity mode). Acetal molds of 3.5 mm internal diameter and 2 mm height were placed over the treated areas, filled with a resin composite (Tetric Evoceram, Ivoclar-Vivadent, Schaan, Liectenstein) in two 1 mm increments and light-cured for 20 s each. All the specimens were stored in water for 1 week at 37 °C and then subjected to shear loading at the substrate-composite interface with the notched-edge blade method [18 ] in a universal testing machine (Tensometer 10, Monsanto, Swidon, UK) operated at a crosshead speed of 0.5 mm/min. The debonded surfaces both for the alloy and zirconia specimens were examined at 10× magnification under a stereomicroscope (M80, Leica, Wetzlar, Germany) to characterize the failure mode (Type I: Adhesive failure, Type II: Cohesive resin failure and Type III: Mixed type I and II failure).

All cavities were acid-etched using phosphoric acid (Top Dent Etch gel 38%, DAB Dental, Sweden) using all etch techniques for 15 seconds and thoroughly washed by water spray for 10 seconds blot excess water via cotton pell. Then, two conclusive layers of single-bottle adhesive (Clearfil SE bond, Kuraray Dental, New York, USA) were applied, gently air sprayed for 5 seconds, and light-cured for 20 seconds through the use of a visible-light curing device (400-1000 mW/cm²) continuous mode. Handling of all materials was carried out based on the manufacturer's instructions. Then, all the prepared cavities were filled in one layer with a shade A1 nanohybrid composite resin (Tetric Evoceram, Ivoclar Vivadent, New York, USA) using a nonstick titanium-coated applicator and light-cured with LED light cure device (LED Flash max P3 Hexagon, Denmark) with an output power of 400-1000 mW/cm² for 20 sec. All the restored teeth were stored for one week in 37°C distilled water inside an incubator. After that, the samples were exposed to thermocycling and subjected to 500 cycles in between 5°C and 55°C, with 30 sec dwell time [13 (link)].