Research Article Effect of Nd:YAG Laser with/without Graphite Coating on Bonding of Lithium Disilicate Glass-Ceramic to Human Dentin Amjad Abu Hasna , 1 Stephanie Semmelmann, 2 Fernanda Alves Feitosa , 3 Danilo De Souza Andrade, 2 Franklin R Tay , 4 and Cesar Rog´ erio Pucci 2 1 Department of Restorative Dentistry, Endodontics Division, Institute of Science and Technology, Sao Paulo State University (UNESP), Sao Jose dos Campos, SP, Brazil 2 Department of Restorative Dentistry, Institute of Science and Technology, Sao Paulo State University (UNESP), Sao Jose dos Campos, SP, Brazil 3 São Lucas University, Avenida Da Saudade 26 Caçapava, SP, Brazil 4 Department of Endodontics, e Dental College of Georgia, Augusta University, Augusta, GA, USA Correspondence should be addressed to Cesar Rog´ erio Pucci; cesar@fosjc.unesp.br Received 22 November 2020; Revised 24 February 2021; Accepted 4 March 2021; Published 16 March 2021 Academic Editor: Alessandro Leite Cavalcanti Copyright © 2021 Amjad Abu Hasna et al. is is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. is study evaluated the effect of different surface treatments on the tensile bond strength between lithium disilicate glass- ceramics, resin cement, and dentin. Fifty truncated cone-shape glass-ceramics were divided into five groups (n � 10): G1, control: 10% hydrofluoric acid (HF); G2, Nd:YAG laser+silane; G3, Sil+Nd:YAG laser; G4, graphite+Nd:YAG laser+Sil; and G5, graphite + Sil + Nd:YAG laser. Fifty human third-molars were cut to cylindrical shape and polished to standardize the bonding surfaces. e glass-ceramic specimens were bonded to dentin with a dual-cured resin cement and stored in distilled water for 24 h at 37 oC. Tensile testing was performed on a universal testing machine (10 Kgf load cell at 1mm/min) until failure. e bond strength values (mean ± SD) in MPa were G1 (9.4 ± 2.3), G2 (9.7 ± 2.0), G3 (6.7 ± 1.9), G4 (4.6 ± 1.1), and G5 (1.2 ± 0.3). Nd:YAG laser and HF improve the bond strength between lithium disilicate glass-ceramics, resin cement, and dentin. e application of a graphite layer prior to Nd:YAG laser irradiation negatively affects this bonding and presented inferior results. 1. Introduction Glass-ceramics were introduced into dentistry as early as 1885 [1] and have improved substantially since then. Despite their esthetic advantages, glass-ceramics are brittle and highly susceptible to fracture [2]. To date, glass-ceramics have improved significantly in their mechanical properties [3]. ere is an increasing tendency to use lithium disilicate glass-ceramics in restorative dentistry because of its com- bined esthetic values, optimal mechanical properties, and excellent optical properties [4,5]. Different surface treatment techniques have been pro- posed for improving the bond strength between silicate- based glass-ceramics and resin cements. Hydrofluoric acid (HF) etching is the most commonly used for conditioning silicate-based glass-ceramic surfaces [6]. As well, neodym- ium-doped yttrium aluminum garnet (Nd:YAG) lasers are used to increase the roughness of glass-ceramic surfaces and improve their adhesion to resin cements [7,8]. is is achieved through the creation of microporosities, increase in surface energy, and improved wetting by the resin cement [8]. e wavelength of Nd:YAG laser is 1064 nm, which is in the invisible nonionizing infrared range. Emission in the pulsed mode is well absorbed by pigmented chromophores, present in soft tissues. Because absorption by hard dental tissues is very limited, clinical procedures involving the use of Nd:YAG lasers may be performed in the vicinity of enamel, dentin, and cementum without creating undue thermal damage [9]. Hindawi International Journal of Dentistry Volume 2021, Article ID 6677159, 7 pages https://doi.org/10.1155/2021/6677159