RESEARCH ARTICLE Dentin bond strength and nanoleakage of the adhesive interface after intracoronal bleaching Vanessa Cavalli 1 | Maicon Sebold 1 | Mirela Sanae Shinohara 2 | Patrícia N  obrega Rodrigues Pereira 3 | Marcelo Giannini 1 1 Department of Restorative Dentistry, Operative Dentistry Division, Piracicaba Dental School, University of Campinas, Bairro Arei~ ao, Piracicaba, SP, 13414-018, Brazil 2 Department of Restorative Dentistry, Dental Materials Division, Piracicaba Dental School, University of Campinas, Bairro Arei~ ao, Piracicaba, SP, 13414-018, Brazil 3 Department of Restorative Dental Sciences, Operative Dentistry Division, College of Dentistry, University of Florida, Gainesville, Florida 32610 Correspondence Vanessa Cavalli, Department of Restorative Dentistry, Operative Dentistry Division, Piracicaba Dental School, University of Campinas, Av. Limeira, 901 Bairro Arei~ ao, Piracicaba, SP, 13414-018, Brazil. Email: cavalli@unicamp.br Funding information S~ ao Paulo Research Foundation (FAPESP), Grant/Award Number: 03/07900-5; Coordination for the Improvement of Higher Education Personnel (CAPES), Grant/Award Number: 3668/05-3 Review Editor: Prof. Alberto Diaspro Abstract This study evaluated dentin bond strength (BS) and nanoleakage of non- and pre-etched dentin immediately (T 0 ,), 7 days (T 7 ), and 14 days (T 14 ) after bleaching. Bovine incisors (150) were selected and half of them submitted to intrapulpal dentin etching (e). Non- and pre-etched dentin were sub- jected to the following (n 5 15): no bleaching/control (C); 35% carbamide peroxide (CP); 35% hydrogen peroxide (35% HP); 25% hydrogen peroxide (25% HP); and sodium perborate (SP). Bleaching agents were applied to the pulp chamber four times within a 72-h interval. Afterwards, pulp chamber dentin was prepared for the BS test at different evaluation times (n 5 5): T 0 ,T 7 , and T 14 . Composite blocks were built on pulp chamber and sectioned in slices. Slices were reduced to an hour-glass shape with a cross-sectional area of 0.8 mm 2 and submitted to microtensile BS test. Two additional specimens for each group were prepared for nanoleakage evaluation by transmis- sion electron microscopy (TEM). Results were analyzed by ANOVA (two-way) and Dunnett’s test (p < .05). BS decreased immediately after intracoronal bleaching for both sound and pre-etched dentin (p < .05). At T 14 , the BS of non-etched bleached dentin increased for all groups, whereas the pre-etched SPe group presented BS similar to the Ce. Nanoleakage within the hybrid layer was perceptible immediately after bleaching, although a decrease in nanoleakage was observed for all groups at T 14 . Adhesive restorations should be performed 7–14 days after bleaching, according to the bleaching agent used. Intracoronal bleaching should be performed preferably with sodium per- borate if previous dentin etching is applied. KEYWORDS bond strength, intracoronal bleaching, nanoleakage, transmission electron microscopy 1 | INTRODUCTION The walking bleach technique is the most common intracoronal proce- dure used to lighten nonvital teeth (Plotino, Buono, Grande, Pameijer, & Somma, 2008). The technique consists of a mixture of sodium perborate and distilled water, which is confined to the pulp chamber and sealed with provisional cement for 7 days (Plotino et al., 2008). Other bleaching agents such as 25–35% hydrogen peroxide (HP) and 35% carbamide peroxide have emerged as popular and effective agents for intracoronal bleaching (Cavalli et al., 2009; G€ okay, Tunçbilek, & Ertan, 2000). The effectiveness of bleaching relies on the oxidation process of the agents involved. Hydrogen peroxide (H 2 O 2 ), the active com- pound, is released during the decomposition of sodium perborate (NaBO 3 4H 2 O) and carbamide peroxide (CH 6 N 2 O 3 ). The mechanism of bleaching is thought to occur due to the release of free radicals from the decomposition of hydrogen peroxide. Hydrogen peroxide can produce a number of different active oxygen species depending on the reaction conditions (temperature, pH, light, and presence of transition metals). Free radicals, such as hydroxyl (OH), attack organic compounds (chromophores) that possess extended conju- gated chains of alternating single or double bonds. Bleaching of the chromophore can occur by cleavage or oxidation of the conjugated chain (Joiner, 2006). Although sodium perborate, 35% hydrogen peroxide, and 35% carbamide peroxide are effective as intracoronal bleaching agents (Kaneko, Inoue, Kawakami, & Sano, 2000), they are able to promote Microsc Res Tech. 2018;1–9. wileyonlinelibrary.com/journal/jemt V C 2018 Wiley Periodicals, Inc. | 1 Received: 26 July 2017 | Revised: 18 December 2017 | Accepted: 6 January 2018 DOI: 10.1002/jemt.22995