Optical Properties of Zirconia Monolithic Crowns Constructed Using Speed Sintering Cycle

Purpose: This study examined the effect of change in sintering time on the optical properties of monolithic zirconia crowns using ZirCAD Prime. Materials and methods: A Sound premolar was scanned using optical oral scanner. The scanned premolar was digitally prepared to receive zirconia restoration using Exocad software following standard preparation guidelines for ceramic restorations. 3D printed resin master die was produced. An impression was made for the 3D printed master die using polyvinylsiloxane impression material then poured using epoxy resin. The procedure was repeated to obtain 16 epoxy resin models. Sixteen crowns were produced by CADCAM system from ZirCAD Prime blank shade A2 with 16 mm thickness. Samples were divided into two groups according to sintering time (n=8). Group (A): crowns were sintered using normal sintering cycle for 9h and 50 min. Group (B): crowns were sintered using speed sintering cycle for 2h and 26 min. After sintering the internal surfaces of both groups were abraded with 50 μm Al2O3 particles. Optical properties including Translucency Parameter (TP) and change in color (ΔE) of samples were determined using spectrophotometer. Obtained values were statistically analyzed. Results: Regarding change of color evaluation mean ∆E values were below 3.0 which is considered “clinically imperceptible”. There was also no significant difference in translucency parameter between both groups. Conclusion: ZirCAD Prime speed sintering cycle will have no perceived effect on color and translucency of the final restoration.