Influence of Surface Treatment on the Shear Bond Strength of Ceramics Fused to Cobalt–Chromium Geraldo H. L. Lombardo, DDS, MSc, 1 Renato S. Nishioka, DDS, MSc, PhD, 2 Rodrigo O. A. Souza, DDS, MSc, PhD, 3 Silvia M. A. Michida, DDS, MSc, PhD, 4 Alberto N. Kojima, DDS, MSc, PhD, 1 Alfredo M. M. Mesquita, DDS, MSc, PhD, 5 & Leonardo Buso, DDS, MSc, PhD 5 1 S˜ ao Jose dos Campos Dental School, S ˜ ao Paulo State University (UNESP), S ˜ ao Paulo, Brazil 2 Professor, Department of Dental Materials and Prosthodontics, S ˜ ao Jose dos Campos Dental School, S˜ ao Paulo State University (UNESP), S ˜ ao Paulo, Brazil 3 Adjunct Professor, Department of Restorative Dentistry, Federal University of Para´ ıba (UFPB), Para´ ıba, Brazil 4 Graduate Student, Department of Prosthodontics, S ˜ ao Jose dos Campos Dental School, S ˜ ao Paulo State University (UNESP), Brazil 5 Paulista University Dental School (UNIP), S ˜ ao Paulo, Brazil Keywords Shear bond strength; metal–ceramic system; surface treatment. Correspondence Rodrigo Oth ´ avio Assunc ¸˜ ao de Souza, Federal University of Para´ ıba, Department of Restorative Dentistry, Center of Health Science, Rua Praia de Guajir ´ u, 9215, Ponta Negra, Natal/RN, Brazil, Cep: 59.092-220. E-mail: roasouza@yahoo.com.br Accepted: February 26, 2009 doi: 10.1111/j.1532-849X.2009.00546.x Abstract Purpose: To evaluate the influence of surface treatment on the shear bond strength between a Co-Cr alloy and two ceramics. Materials and Methods: Forty-eight metal cylinders were made (thickness: 4 mm, height: 3.7 mm) according ISO TR 11405. The 48 metallic cylinders were divided into four groups (n = 12), according to the veneering ceramic (StarLight Ceram and Duceram Kiss) and surface treatments: air-particle abrasion with Al 2 O 3 or tungsten drill (W). Gr1: StarLight + Al 2 O 3 ; Gr2: StarLight + W; Gr3: Duceram + Al 2 O 3 ; and Gr4: Duceram + W. The specimens were aged using thermal cycling (3000×, 5 to 55 ◦ C, dwell time: 30 seconds, transfer time: 2 seconds). The shear test was performed with a universal testing machine, using a load cell of 100 kg (speed: 0.5 mm/min) and a specific device. The bond strength data were analyzed using ANOVA and Tukey’s test (5%), and the failure modes were analyzed using an optical microscope (30×). Results: The means and standard deviations of the shear bond strengths were (MPa): G1 (57.97 ± 11.34); G2 (40.62 ± 12.96); G3 (47.09 ± 13.19); and G4 (36.80 ± 8.86). Ceramic (p = 0.03252) and surface treatment (p = 0.0002) significantly affected the mean bond strength values. Conclusions: Air-particle abrasion with Al 2 O 3 improved the shear bond strength between metal and ceramics used. Although the trend in modern dentistry is to use metal-free restorations, when clinically analyzed, metal–ceramic restora- tions are still the most frequently used for making fixed par- tial dentures (FPDs) and single crowns, as these restorations present excellent clinical performance, low cost when com- pared with metal-free restorations, a simple cementation tech- nique (zinc phosphate cement), and in the great majority of restorative treatments, natural reproduction of the lost denti- tion. Due to the high cost of precious alloys in the 1970s and progress made in ceramic technology, the use of basic metal alloys as infrastructure materials for FPDs increased consider- ably, 1 particularly nickel–chrome- (Ni-Cr) and cobalt–chrome- (Co-Cr)based alloys; however, because of adverse effects, such as allergies to the material, shown particularly by alloys con- taining nickel and beryllium, the use of more biocompati- ble 2,3 Co-Cr-based alloys has been suggested, since they have shown excellent marginal integrity and an absence of ad- verse reactions. 2 Furthermore, these alloys allow treatments of excellent quality, because they have very satisfactory me- chanical properties, such as hardness, elasticity, and tensile strength. 1 Even though they have a metal infrastructure, these restora- tions are subject to failures that could occur predominantly at the interface between the metal and the porcelain. 4 Three possibilities of retention for porcelain bonded to metal can be observed: Van der Waals forces, micromechanical retention, and chemical bonding, with chemical bonding being the main determinant of union, as characterized by the direct transfer of Journal of Prosthodontics 19 (2010) 103–111 c  2009 by The American College of Prosthodontists 103