Comparison of 2.5% Sodium Hypochlorite and 2% Chlorhexidine Gel on Oral Bacterial Lipopolysaccharide Reduction from Primarily Infected Root Canals Brenda P.F.A. Gomes, PhD,* Frederico C. Martinho, DDS,* and Morgana E. Vianna, PhD* † Abstract Introduction: This clinical study was conducted to compare the efficacy of chemomechanical preparation with 2.5% sodium hypochlorite (NaOCl) and 2% chlo- rhexidine (CHX) gel on eliminating oral bacterial lipo- polysaccharide (LPS) in teeth with pulp necrosis and apical periodontitis. Methods: Fifty-four root canals were selected. Samples were collect before (s1) and after chemomechanical preparation (s2). Teeth were randomly divided into groups: GI, 2.5% NaOCl (n = 27) and GII, CHX gel (n = 27). Limulus amebocyte lysate assay was used to quantify endotoxins. Results: Endo- toxin was present in 100% of the samples investigated, with a median value of 272 endotoxin units (EU)/mL (GI) and of 152.46 EU/mL (GII). As a result of chemomechan- ical preparation, LPS content was reduced to a median value of 86 EU/mL (GI) and 85 EU/mL (GII). Higher percentage value of endotoxin reduction was found in GI (P < .05). Conclusions: The 2.5% NaOCl and 2% CHX gel were not effective in eliminating endotoxin from the primarily infected root canals. (J Endod 2009;35:1350–1353) Key Words Bacteria, chlorhexidine, endotoxin, oral bacterial LPS, root canal, sodium hypochlorite E ndotoxin liberated by gram-negative bacteria has been detected in primary root canal infections (1–5). High levels of endotoxin have been associated with the devel- opment of spontaneous pain (1, 3, 6, 7) and clinical symptoms such as tenderness to percussion (3, 5) and pain on palpation (5). Because of the high toxicity of endotoxin in vivo (2, 8, 9), developing periapical inflammation and alveolar bone resorption, and in vitro (10–12), stimulating cells to release proinflammatory cytokines that lead to tissue destruction (13, 14), its removal/ neutralization from infected root canals during endodontic treatment seems to be important for the healing process of periapical tissues. Therefore, to achieve an optimal disinfection of the root canal system, endodontic treatment should not rely only on eliminating microorganisms and substrates (15) but also on inactivating or eliminating lipopolysaccharide (LPS). Several chemical substances have been tested for the inactivation of endotoxin (16–22), particularly sodium hypochlorite (NaOCl) (5, 18–22), the most widely used endodontic irrigant, and chlorhexidine (CHX) (4, 18–20, 22), a potential auxil- iary chemical substance applied in endodontic treatment. Most in vitro (23–26) and in vivo (27–30) studies evaluating antimicrobial action of NaOCl and CHX assessed their ability on reducing or eliminating bacterial load from infected root canals. However, no clinical study had compared their potential on eliminating LPS from root canal infection. Therefore, the present clinical study was conducted to compare the efficacy of che- momechanical preparation with either 2.5% NaOCl or 2% CHX gel on eliminating oral bacterial LPS in teeth with pulp necrosis and apical periodontitis. Material and Methods Fifty-four patients at the Piracicaba Dental School, Piracicaba, SP, Brazil, who needed endodontic treatment were included in this research. The age of the patients ranged from 18–62 years. Samples were collected from 54 root canals with pulp necrosis and showing evidence of apical periodontitits in radiographs before and after chemomechanical preparation. The selected teeth (1 tooth per patient) were uniradic- ular, containing a single root canal; their pulp chamber was without visual communi- cation with the oral fluid; they presented with necrotic pulp tissue and showed radiographic evidence of periapical periodontitis but an absence of periodontal disease. None of the patients reported spontaneous pain. A detailed dental history was ob- tained from each patient. Patients who had received antibiotic treatment during the last 3 months or who had a general disease were excluded from this research. The Human Volunteers Research and Ethics Committee of the Piracicaba Dental School approved a protocol describing the specimen collection for this investigation, and all patients signed an informed consent document to participate in this research. All materials, including the paper points used in this study, were heat sterilized at 200  C for 4 hours, becoming apyrogenic. The method followed for the disinfection of the operative field has been described previously (3–5). Briefly, the teeth were isolated with a rubber dam. The crown and the surrounding structures were disinfected with 30% H 2 O 2 (volume/volume [V/V]) for 30 seconds followed by 2.5% NaOCl for an additional 30 seconds. Subsequently, 5% sodium thiosulfate was used to inactivate the irrigant. The sterility of the external From the *Department of Restorative Dentistry, Endodontic Division, Piracicaba Dental School, State University of Campi- nas, Piracicaba, SP, Brazil; and † UCL Eastman Dental Institute, Unit of Endodontology, University College London, London, United Kingdom. Address requests for reprints to Dr Brenda P. F. A. Gomes, Faculdade de Odontologia de Piracicaba, UNICAMP, A ´ rea de Endodontia, Avenida Limeira, 901, Piracicaba, Sa ˜ o Paulo 13414-903, Brazil. E-mail address: bpgomes@fop.unicamp.br. 0099-2399/$0 - see front matter Published by Elsevier Inc. on behalf of the American Association of Endodontists. doi:10.1016/j.joen.2009.06.011 Clinical Research 1350 Gomes et al. JOE — Volume 35, Number 10, October 2009