Evaluation of the Bond Strengths Between Dental Ceramics and Co-Cr Frameworks Made with Digital and Conventional Techniques

Purpose: To evaluate the influence of different Co-Cr framework manufacturing techniques on the bond strength between metal and two types of veneering ceramics with and without a metal primer. Materials and Methods: A total of 72 metal specimens were fabricated using the same Co-Cr alloy (Keramit NP, Nobil Metal) with three different techniques: ingots for casting (Keramit NP); disks for CAD/CAM milling (sinergia disk Keramit NP); and powder for selective laser melting (SLM, Keramit NP-S). Each of the 24-specimen groups was divided into two subgroups, according to the application, or lack thereof, of Nobil Metal Bonding (NMB). Two different veneering ceramic systems were used: Ceramco iC (Dentsply Sirona) and Noritake Super Porcelain EX-3 (Noritake). The bond strength of the metal-ceramic system was evaluated using the three-point bending test and the modality of failure with SEM analysis. Three-way ANOVA with interactions was used to evaluate the influence of the metal production process, the presence or absence of the bonding agent, and the type of veneering ceramic on ceramic-metal adhesion. Results: All specimens exceeded the minimum bond strength of 25 MPa required by ISO Standard 9693-1:2012. The highest values of adhesion were registered for specimens manufactured with casted metal/Noritake veneering ceramic (40.59 +/- 7.30 MPa). The lowest values were registered for specimens manufactured with CAD/CAM metal/NMB/ Ceramco iC veneering ceramic (29.47 +/- 3.38 MPa). Conclusions: The fabrication method and the type of veneering ceramic had a significant influence on the mean bond strength. The application of the NMB did not show an influence on bond strength.