2.5. Fabrication of Crowns
HT
HEAT
All samples were digitally scanned using the Cercon eye scanner (DeguDent GmbH, Hanau, Germany) and designed by the software of Cercon art 3.2 (DeguDent GmbH, Germany) to receive Cercon HT full-contoured crowns. The milling process was accomplished with a Cercon Xpert machine (DeguDent GmbH, Germany) after selecting a zirconia bur and a Cercon disc (DeguDent GmbH, Germany) containing 94.5% pure zirconium. To attain full strength, sintering was accomplished in the dental lab in a Cercon heat plus P8 machine (Dentsply Sirona, NC, USA) set at 8 h and 30 min by a dental technician with a sintering device Cercon Heat (DeguDent GmbH, Germany). The visually unacceptable teeth and those with margin damages were rejected, and another coping was made as needed. The intaglio surface of the Zi crowns were pretreated, mechanically, through air blasting with alumina oxide and cleaned with an alkaline agent, Ivoclean (ivoclar vivadent, Schaan, Liechtenstein), before cementation.