Crown cementation
The received crown restoration was inspected and checked for fitness and adaptation. Then, all the prepared samples were rinsed with water spray and lightly air-dried. Next, the inner surfaces of the crowns were etched with 5% hydrofluoric acid for 20 s; then, they were rinsed off and dried. After that, Prime & Bond® adhesive (Dentsply, Switzerland) was applied onto the pretreated crown surface for salinization. Subsequently, the crown was filled with the Rely Xtm U200 Automix self-adhesive resin cement; then, the height was seated firmly on the core. After 3 min, the excess glue was removed by a sharp explorer. Finally, all cemented specimens were stored in distilled water at 37° C in an incubator for 24 h before being subjected to thermocycling (ISO/TS 11,405, 2003).