Residues of Different Gel Formulations on Dentinal Walls: A SEM/EDS Analysis ANGELA LONGO DO NASCIMENTO, 1 * FERNANDA HOFFMANN BUSANELLO, 1 MARCUS VIN  ICIUS REIS S  O, 1 MILTON CARLOS KUGA, 2 JEFFERSON RICARDO PEREIRA, 3 AND FABIANA SOARES GRECCA 1 1 Department of Conservative Dentistry, Federal University of Rio Grande Do Sul, Porto Alegre, Rio Grande do Sul, Brazil 2 Department of Restorative Dentistry, School of Dentistry, S~ ao Paulo State University (UNESP), Araraquara, S~ ao Paulo, Brazil 3 Department of Prosthodontics, Dental School, University of Southern Santa Catarina, Tubar~ ao, Santa Catarina, Brazil KEY WORDS endodontics; sodium hypochlorite; chlorhexidine; EDTA; electron probe microanalysis ABSTRACT The aim of this study was to evaluate the presence of residues of sodium hypo- chlorite gel, chlorhexidine gel, and EDTA gel on dentinal walls after canal preparation through chemical SEM- elemental chemical microanalysis (EDS) analysis. Forty-eight single-rooted teeth were selected. They had their crowns sectioned and were instrumented with a reciprocat- ing system. The canals were irrigated with 5 mL of saline solution during root canal preparation. After instrumentation, the root canals were irrigated with 3 mL 17% EDTA followed by 1 min of ultrasonic passive activation (33 20 sec) to remove the smear layer, and then irrigated with 3 mL of saline solution. The specimens were randomized into three groups (n 5 12) according to the chemical substance that filled the root canal for 30 min: GI: 5.5% sodium hypochlorite gel; GII: 2% chlorhexidine gel; GIII: 24% EDTA gel; Negative control group: no substance was used. Then, the root canals were irrigated with 6 mL of saline solution followed by 1 min of ultrasonic passive activation (33 20 sec). After ultrasonic activation, the canals were irrigated with 2 mL saline. The roots were sectioned, and the percentage of each chemical element present in the samples was analyzed through chemical SEM-EDS microanalysis. All experimental groups showed a significantly higher percentage of chemical elements (Na and/or Cl) than the control group (P < 0.03). This in vitro study has shown that, regardless of chemical solutions used even after the final irrigation protocol, chemical residues of different substances remained attached to the root canal walls. Microsc. Res. Tech. 78:495–499, 2015. V C 2015 Wiley Periodicals, Inc. INTRODUCTION The choice of irrigating substances is important because there are differences in their efficacy as lubri- cants during instrumentation to flush debris, smear layer, and bacteria out of the canal (Zand et al., 2010). Moreover, the irrigating solution must play a major role in the elimination of microorganisms and tissue biocompatibility dissolution (Gomes et al., 2001). There is no single solution that has all these properties (Rossi-Fedele et al., 2012). Among the auxiliary chemicals used in endodontics during the chemical–mechanical preparation, sodium hypochlorite at different concentrations has been the most commonly used because of its broad antimicrobial spectrum, and its unique ability to dissolve the remaining necrotic tissue (Moreira et al., 2009; Zehnder, 2006). However, the incorrect use can cause serious complications. The most common complication is accidental injection into the periapical tissues (Sabala and Powell, 1989). Chlorhexidine gluconate is an alternative substance that has been used in endo- dontics, which is preferred as irrigating solutions dur- ing root canal treatment of deciduous teeth (Onc¸ag et al., 2003), given that it is less toxic than sodium hypochlorite and still plays a residual antibacterial role (Ercan et al., 2004; Onc¸ag etal., 2003). Another alternative for the prevention of accidents caused by extrusion of irrigating solutions is gel for- mulations (Kim et al., 2013). Zand et al. (2010) have demonstrated that there are no significant differences between sodium hypochlorite solution and gel in the smear layer removal in three thirds of root canal, which shows that the use of NaOCl gel can be effective, besides eliminating the side effects of the sodium hypo- chlorite solution. Valera et al. (2010) showed that chlo- rhexidine gel presented higher cleaning effect on the dentin compared with liquid chlorhexidine. However, chlorhexidine is unable to dissolve necrotic tissue debris (Naenni et al., 2004); at the same time, due to its viscosity, the gel seems to compensate for chlorhexi- dine’s inability to dissolve pulp tissue by providing a better mechanical cleansing of the root canal, remov- ing dentin debris and remaining tissues provided by a lubricating action during instrumentation (Ferraz et al., 2001). Kim et al. (2013) suggests that the *Correspondence to: Angela Longo do Nascimento, Faculdade de Odontologia, Universidade Federal do Rio Grande do Sul, Rua Ramiro Barcelos, 2492–Bairro Santa Cec  ılia, Porto Alegre, RS, Brasil, CEP 90035-003. E-mail: angelalongo@gmail.com REVIEW EDITOR: Prof. Alberto Diaspro Received 1 February 2015; accepted in revised form 9 March 2015 DOI 10.1002/jemt.22500 Published online 24 March 2015 in Wiley Online Library (wileyonlinelibrary.com). V V C 2015 WILEY PERIODICALS, INC. MICROSCOPY RESEARCH AND TECHNIQUE 78:495–499 (2015)