Abstract
Abstract Background and objectives: the success and durability of fused to metal restorations (PFM) is primarily dependent on the adherence strength between metal substructures and porcelain materials. The nature of the bond strength between dental porcelain and metal alloys has been the subject of considerable discussion in the dental literature. Nonprecious alloys have been used for decades as frameworks in the production of PFM prosthesis. The most common types are Ni-Cr and more recently Co-Cr alloys. With the increase of innovative techniques, metals with different compositions have been introduced to the market. Thus, the purpose of this study was to evaluate and compare the tensile bond strength of a dental ceramic to 3 commercially available alloys: one type of Ni-Cr and two types of Co-Cr alloys. Materials and methods: in this study a total of thirty samples were wax printed using a rapid prototyping machine. Each ten specimens were cast from one commercial alloy using the lost-wax technique (Wiron®99Ni-Cr, Wirobond®280 Co-Cr and d.SIGN®30 Co-Cr). Two layers of opaque and a measured thickness of dentin were applied to the three metal groups. The tensile bond strength test was carried out with an across head speed of 1.0 mm/min. A one-way ANOVA test was conducted to determine the ultimate tensile bond strength (MPa) of the tested groups. Stereomicroscope and SEM were used to examine the fracture surfaces of the metal groups. Results: the mean (SD) bond strengths (MPa) of the results were: 32.3 (9.7) for Wirobond; 25.4 (6.8) for d.SIGN and 24.7 (9.7) for Wiron®99. There was no significant difference found between the mean bond strength for the three metal alloy groups (P > 0.05). The bond failure was predominantly at the interface between Co-Cr alloys and ceramic, whereas, cohesive failure was observed within the ceramic itself for Ni-Cr group. Conclusion: the bond strength of dental porcelain bonded to Co-Cr alloys showed acceptable clinical results unlike Ni-Cr alloys. Therefore, Co-Cr alloys seem a promising alternative to Ni-Cr alloys in the production of PFM restorations. Keywords: Bond strength, ceramic, Co-Cr alloys, Ni-Cr alloys and tensile test.