Influence of Different Sintering Protocols on Translucency and Fracture Resistance of Monolithic Zirconia Crowns

Document Type : Original Article

Authors

1 Oral and Maxillofacial Prosthodontic Department, Faculty of Dentistry, King Abdulaziz University, Jeddah, Kingdom of Saudi Arabia.

2 Lecturer Fixed Prosthodontics Faculty of Oral and Dental Medicine Future University in Egypt, Cairo, Egypt

Abstract

Purpose : The current study investigated the effect of different sintering protocols (long, speed and high- speed cycles) on translucency and fracture resistance of monolithic zirconia crowns. Materials and Methods: 30 monolithic zirconia crowns were CAD/CAM fabricated from translucent BruxZir zirconia blanks. The crowns were divided into three groups (n=10 each) according to the sintering protocols(temperature & speed); Group (I): samples sintered by long sintering cycle (1510°C , 120 min holding time and 8 hours total cycle time), Group (II): speed sintering ( 1540°C , 25 min holding time and 2 hours total cycle time) and Group (III): high-speed sintering (1580°C, 10 min holding time representing the total firing cycle).Translucency parameter (TP) and Contrast Ratio (CR) were measured using a spectrophotometer, then compressive load was applied till fracture in a universal testing machine. One representative disc sample (10mm diameter x 1 mm thickness) was fabricated and sintered according to the parameters of each group and analyzed by scanning electron microscope. Collected data were statistically analyzed. Results: Sintering speed had a statistically significant effect on (TP),(CR) and fracture resistance means. Long cycle showed the statistically significantly highest (TP) and lowest (CR) mean values. The high-speed cycle recorded the statistically significantly highest fracture resistance mean values. Conclusion: Shortening the sintering cycle significantly decreased translucency and increased fracture resistance of monolithic zirconia crowns. Regarding Translucency Perception Threshold ,speed cycle can be recommended for sintering of BruxZir monolithic zirconia crowns.

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