Effect of Chemical Substances in Removing Methylene Blue After Photodynamic Therapy in Root Canal Treatment Erica dos Santos Carvalho, M.Sc., 1 Isabel Mello, D.D.S., M.Sc., Ph.D., 2 Silvio Jose ´ Albergaria, M.Sc., Ph.D., 3 Sandra Ma ´ rcia Habitante, M.Sc., Ph.D. 1 Jose ´ Luiz Lage-Marques, M.Sc., Ph.D., 1 and Denise Pontes Raldi, M.Sc., Ph.D. 1 Abstract Background and objective: The disadvantage of photodynamic therapy (PDT) is in the photosensitizing agents that may stain the tooth structure. There is no register of PDT studies evaluating protocols to minimize that concern. The present study evaluated the efﬁciency of chemical adjuncts in methylene blue dye (MB) removal after PDT. Materials and methods: Forty single-rooted teeth, after root canal preparation, were ﬁlled with 0.01% MB for 5 min, and irradiated with diode laser 660 nm at 40 mW for 240 sec (total energy 9.6 J). The specimens were divided into four groups (n ¼ 10), according to the chemical adjuncts used for dye removal: (a) 2.5% sodium hypochlorite (NaOCl); (b) 2.5% NaOCl þ Endo-PTC cream; (c) 70% ethyl alcohol and (d) saline (control). The crowns were sectioned and ﬁxed in a device. Photographs were taken before the PDT (T0), immediately after (T1) and upon dye removal (T2). The chromatic alterations were evaluated using Adobe Photoshop and K values were determined in four ﬁxed points of each crown. Results: K values (dental staining) increased in all groups when comparing T0 and T1. The effectiveness of the tested adjuncts was, in decreasing order: G1 (3.11) > G2 (2.97) > G3 (1.28) > G4 (1.19), not observing signiﬁcant statistical differences ( p < 0.05) between G1 and G2 and also between G3 and G4. Conclusions: Protocols to remove photosensitizing dyes should be applied after PDT in order to minimize dental stain. The protocols tested in this study by using 2.5% NaOCl, associated or not with Endo-PTC cream, were effective in avoiding tooth staining caused by MB during PDT. Introduction T he purpose of endodontic therapy is to eliminate bacterial infection in the root canal system, allowing apical healing. If correctly performed, root canal therapy is a procedure with a high rate of successful outcome (>97%). 1 However, because of the anatomic complexity of the root canal system, achieving complete debridement and disinfec- tion is challenging, and might lead to establishment or per- sistence of post-treatment apical periodontitis. 2,3 When endodontic treatment fails, resistant microorgan- isms are usually present. Enterococcus faecalis is a gram- positive facultative anaerobic bacterium frequently associ- ated with endodontic treatment failure 4 that forms intra- and extraradicular bioﬁlms. This bioﬁlm pattern protects the bacteria from the action of intracanal irrigants and medica- ments. 5 For this reason, research has sought alternative procedures to those conventionally used during root canal treatment with the attempt to improve the outcome, espe- cially in those cases of persistent apical inﬂammation. Techniques, instruments, and equipments have been de- veloped to improve clinical work and achieve high success rate in treatment. Since the early 1990s, several studies have been done on the impact of low-intensity lasers in end- odontics. 6,7 Promising results have been shown in microbial reduction in the root canal system by photodynamic therapy (PDT). 3,8-10 Photodynamic inactivation of microorganisms is based upon the concept that a dye, known as a photosensi- tizer, should be localized preferentially in the bacteria and not in the surrounding tissues or cells, and subsequently 1 Department of Dentistry, University of Taubate, Taubate, Sa ˜ o Paulo, Brazil. 2 Department of Restorative Dentistry, Division of Endodontology, University of Manitoba, Winnipeg, Manitoba, Canada. 3 Department of Dentistry, Division of Endodontics, Federal University of Bahia, Salvador, Bahia, Brazil. Photomedicine and Laser Surgery Volume 29, Number 8, 2011 ª Mary Ann Liebert, Inc. Pp. 559–563 DOI: 10.1089/pho.2010.2922 559