2.5% NaOCl- 2% CHX-gel x LPS/ Bacteria in root canals

Endotoxins liberated by Gram-negative bacteria represent one of the main etiologic agents involved in the pathogenesis and perpetuation of periapical inflammation. Because of their high toxicity, their removal/ neutralization during endodontic treatment is important for the healing process of the periapical lesion. Objective: The aim of this work was to evaluate the efficacy of the chemomechanical preparation (CMP) with 2.5% sodium hypochlorite (NaOCl) and 2% chlorhexidine gel (CHX-gel) in reducing bacterial load and LPS from infected root canals. Methods: Thirty-eight root canals from single root teeth, asymptomatic, with pulp necrosis and periapical lesions were selected. A total of 76 samples were recovered from the infected root canals at different sampling times: before (s1) (n=38) and after CMP (s2) (n=38) with 2.5% NaOCl (n=19) and 2% CHX-gel (n=19). Strict anaerobe techniques were used to cultivate as many microorganisms as possible. A quantitative chromogenic Limulus Amebocyte Lysate assay (QLC-1000) was used to determine the amount of LPS. Results: At s1, bacteria (mean: 2.8 x 105 CFU/mL) and LPS (mean: 239.81 EU/mL) were recovered from 100% of the root canals sampled. The CMP with 2.5% NaOCl and 2% CHX-gel were effective in reducing the initial amount of bacteria in 99.78% (mean: 3.6 x 102 CFU/mL) and 99.97% (1.0 x 102 CFU/mL) respectively (p<0.05). At s2, LPS were detected in 100% of the root canals samples. CMP with 2.5% NaOCl and 2% CHX-gel were able to reduce a mean percentual value of 68% (from 228 to 67 EU/mL) and 73% (154 – 47 EU/mL) of the total initial amount of LPS found in root canals at s1 (p<0.05). Conclusion: Our findings indicated that CMP with either 2.5% NaOCl or 2% CHX-gel was moderately effective against bacteria but less effective against LPS in root canal infection.(Supported by FAPESP (05/55695-7, 07/58518-4, 08/06162-4) & CNPq (304282/2003-0, 305437/2006-2)