ORIGINAL ARTICLE Dentin pretreatment with Er:YAG laser and sodium ascorbate to improve the bond strength of glass fiber post Laís Lima Pelozo 1 & Reinaldo Dias Silva-Neto 1 & Silmara Aparecida Milori Corona 1 & Regina Guenka Palma-Dibb 1 & Aline Evangelista Souza-Gabriel 1 Received: 29 January 2018 /Accepted: 29 June 2018 # Springer-Verlag London Ltd., part of Springer Nature 2018 Abstract Root-filled teeth that received fiber posts most frequently fail at the adhesive interface between resin cement and dentin. The objective of this study is to evaluate the effect of Er:YAG laser and/or sodium ascorbate (SA) on bond strength, microhardness of dentin, and penetration depth of cement into dentinal tubules. Forty-eight bovine incisor roots were endodontically treated, post spaces were prepared and equally divided into four groups (n = 12): G1—distilled water (control); G2—10% SA (10 min); G3— Er:YAG laser (150 mJ/4 Hz/40 s), and G4—Er:YAG laser + 10% SA. Glass fiber posts were cemented and roots sectioned into slices. In the first slice, the push-out bond strength (MPa) and failures were analyzed by confocal laser scanning microscope (CLSM). The second slice was subjected to microhardness test (KHN) and CLSM to assess the cement penetration. ANOVA and Tukey test were used for bond strength and microhardness data and Kruskal-Wallis and Dunn tests for the cement penetration (α = .05). The SA-treated samples had higher bond strength (10.02 ± 5.45a), similar to Er:YAG laser (9.91 ± 4.62a) and Er:YAG laser + SA (8.09 ± 4.07a). The least values (P < .05) were found on control (4.02 ± 2.39b). Significant differences were observed on root thirds (P < .05): cervical > middle > apical. There was a predominance of adhesive failures. The microhardness test revealed no differences between groups (P > .05). The experimental groups (G2, G3, and G4) had highest penetration into dentinal tubules when compared to the control (G1). Dentin pretreatments with Er:YAG laser or SA improved bond strength of cement-post-dentin interfaces; however, no synergistic effect of both treatments combined was observed. Keywords Adhesion . Resin cement . Sodium ascorbate . Laser Introduction Root-filled teeth are weakened due to caries, fracture, pulp pathologies, or multiple repeated restorations [1, 2]. They re- quire special considerations for the final restoration, mainly where there has been extensive loss of tooth structure [3, 4]. In these situations, an intracanal post can provide better retention of restoration to compromised roots [2, 5, 6]. Glass fiber posts (GFP) were introduced aiming to improve biomechanical properties as compared to prefabricated metal- lic posts [2, 6, 7]. Studies have supported GFP permits a reg- ular stress distribution of the strength to the root canal, reduce the incidence of root fracture, and provide favorable or repa- rable fracture patterns [8–11]. GFP also has superior esthetics, easier removal, and shorter treatment visits in comparison to posts of different materials [7, 12]. However, there are some reports about failures, includ- ing debonding of the resin cement from intracanal dentin due to hybrid layer degradation. These failures might be attributed to irrigation with sodium hypochlorite (NaOCl) during endodontic treatment. NaOCl acts as a dentin deproteinizing agent, reduces microhardness of intracanal dentin and its by-products hampers the polymerization of adhesive systems [13, 14]. To overcome this problem, different techniques have been proposed to treat intracanal dentin [15–17], and antioxidants such as sodium ascorbate (SA) have been demonstrated to reverse the negative Clinical significance: The pretreatment of post space with Er:YAG laser and/or sodium ascorbate antioxidant agent can transform the intraradicular dentin to a substrate more receptive to adhesive procedures. * Aline Evangelista Souza-Gabriel aline.gabriel@forp.usp.br 1 School of Dentistry of Ribeirão Preto, University of São Paulo, Av. Café s/n, Monte Alegre, CEP 14040-904, Ribeirão Preto, São Paulo, Brazil Lasers in Medical Science https://doi.org/10.1007/s10103-018-2579-5