Microlekage of CAD-CAM Feldspatic, Nano-Resin-Ceramic Crowns Cemented with Resin Cements

Objective: Resistance of machined crowns to microleakage when cemented with new self-adhesive cements has not been fully investigated. This study compared the microlekage between CAD/CAM crowns milled out of conventional feldspatic porcelain and nano resin ceramics, cemented with three different generations of resin cements. Method: Fifty four extracted human premolar teeth were cleaned and mounted in resin blocks. Standard crown preparations with 1-mm circumferential shoulder finish line, flat occlusal surface reduced by 2 mm. Prepared teeth were divided into two equal groups and assigned to either porcelain (Sirona, VITA) or nano-resin-ceramic (Lava Ultimate,3M ESPE) blocks for crown fabrication. Optical impressions were captured for each tooth with the intraoral camera of a CEREC 3D machine. Crowns were designed and milled from both materials. Each group was then subdivided into three subgroups (n = 9) according to cement used (self-adhesive resin cement, RelyX U200, 3MESPE; resin cement with self-etching adhesive,NX3, Kerr Corporation or resin cement with total etching, Variolink II, Ivoclar Vivadent).  Specimens were then stored in water at 37◦C for 24 hours, thermocycled for 3000 cycles between 5◦C and 55◦C, then coated with nail varnish, and immersed in a methylene blue dye solution for 24 hours. Teeth were then rinsed and sectioned mesiodistally and assessed under magnification for microleakage. A five-point scale was used to score degree of microleakage. Data were statistically analyzed with ONE-Way ANOVA. Result: Lava Ultimate crowns showed significantly less microleakage (p< 0.001) compared to Sirona crowns. Rely X U200 showed significantly lower microleakage (p< 0.001) compared to other cements.  Combination of Lava Ultimate and Rely X U200 showed the least microleakage (p< 0.001), compared to the other groups. Conclusion: The microleakage scores were affected by the type of crown material and cements.  Combination of nano-resin-ceramic crown and self-adhesive resin cement gave the lowest microleakage scores.