Effect of Sintering Technique on Shade and Shear Bond Strength of CAD/CAM Monolithic Translucent Zirconia

Introduction: The fabrication of zirconia dental restoration is a time-consuming process due to traditional slow sintering schemes. A speed sintering protocol has been developed to meet the demand for time and cost-effective chair-side CAD/ CAM-produced restorations, as well as to control ceramic microstructures for better translucency. Fast heating and cooling rates, as well as shorter sintering dwell times are known to affect the microstructure and properties of zirconia. Aim of study: This study aimed to investigate and compare between three types of monolithic translucent zirconia in terms of the shade and the shear bond strength of the zirconia samples to adhesive resin cement after conventional and speed sintering. Material and Methods: Three types of zirconia discs were cut into 20 square shaped samples, 10 large square shaped and 10 small square shaped and bonded to each other. Bonded samples were divided according to type of zirconia into 3 groups: Group 1: Dental direct ZX 2 , Group 2: Dental Direct ZW iso, Group 3: Zolid HT+. Each group was subdivided according to sintering technique into 2 subgroups. Shade and shear bond test were measured. Results: The speed sintering of the three types of zirconia showed a lower ΔE values than that showed with the conventional sintering, and among the speed and conventional sintering subgroups Dental Direkt Bio ZX 2 showed the lowest ΔE value and highest shear bond strength value followed by Dental Direct Bio ZW iso and Zolid Ht+. Conclusion: The speed sintering technique of the monolithic translucent zirconia gave better color shade reproduction and higher shear bond strength to resin cement than that of the conventional sintering technique. Dental Direkt ZX 2 produced better color shade reproduction and higher shear bond strength to resin cement than that of the Dental Direkt ZW iso and Zolid Ht+ in speed and conventional sintering technique.