The choice of an irrigating solution for use in infected root canals requires previous knowledge of the microorganisms responsible for the infectious process as well as the properties of different irrigating solutions. Complex internal anatomy, host defenses and microorganism virulence are important factors in the treatment of teeth with asymptomatic apical periodontitis. Irrigating solutions must have expressive antimicrobial action and tissue dissolution capacity. Sodium hypochlorite is the most used irrigating solution in endodontics, because its mechanism of action causes biosynthetic alterations in cellular metabolism and phospholipid destruction, formation of chloramines that interfere in cellular metabolism, oxidative action with irreversible enzymatic inactivation in bacteria, and lipid and fatty acid degradation. The aim of this work is to discuss the mechanism of action of sodium hypochlorite based on its antimicrobial and physico-chemical properties.

Knowing the outcome of root canal treatment (RCT) is determinant to substantiate the clinical decision making process, especially when RCT is weighed against the extraction of natural teeth or replacement by prosthetic elements. The ideal scenario in all clinical situations should combine healing/prevention of disease (apical periodontitis) and the functional retention of the tooth. Understanding the risk factors associated with endodontic failure is a key factor to increase the chances of success. The logical action is to reverse the existing disease, which requires intervention to neutralize the bacterial invasion and disrupt the bacterial biofilm within the complex anatomy. Success is more predictable when the immune host defenses are favorable. However, success has different meanings to the dentist, to the patient and to the tooth itself. The life of an endodontically treated tooth depends on the accuracy of the diagnosis and planning, excellence of disinfection, instrumentation and filling procedures (antimicrobial strategies, root canal shaping and coronal and apical seal) and finally the rehabilitation management. The interpretation of constant or intermittent pain and/or discomfort associated with apical periodontitis (AP) in endodontically treated tooth may be suggestive of endodontic failure. The success features of RCT, namely absence of pain, regression of AP, tight seal of canal and coronal spaces, and recovery of tooth function, must be reevaluated over time. In case of doubt between success and failure, cone beam computed tomography (CBCT) could be indicated for detection and precise localization of AP. The possibility of map reading on CBCT images characterizes the real multidimensional structure, providing accurate information on the presence, absence or regression of AP. The survival of an endodontically treated tooth implies understanding the biological and mechanical outcomes as multifactorial events over the individual's life span. The objective of this review of literature is to discuss relevant factors associated with patient's health, tooth and dentist that could account for a successful RCT.

The objective of this study was to analyze the antimicrobial effect of 2% sodium hypochlorite (NaOCl) and 2% chlorhexidine (CHX) by agar diffusion test and by direct exposure test. Five microorganisms: Staphylococcus aureus, Enterococcus faecalis, Pseudomonas aeruginosa, Bacillus subtilis, Candida albicans, and one mixture of these were used. These strains were inoculated in brain heart infusion (BHI) and incubated at 37ºC for 24 h. For the agar diffusion test (ADT), 18 Petri plates with 20 ml of BHI agar were inoculated with 0.1 ml of the microbial suspensions, using sterile swabs that were spread on the medium, obtaining growth in junction. Fifty-four paper disks (9 mm in diameter) were immersed in the experimental solutions for 1 min. Subsequently, three papers disks containing one of the substances were placed on the BHI agar surface in each agar plate. The plates were maintained for 1 h at room temperature, and then incubated at 37ºC for 48 h. The diameter of microbial inhibition was measured around the papers disks containing the substances. For the direct exposure test, 162 #50 sterile absorbent paper points were immersed in the experimental suspensions for 5 min, and were then placed on Petri plates and covered with one of the irrigant solutions, or with sterile distilled water (control group). After intervals of 5, 10 and 30 min, the paper points were removed from contact with the solutions and individually immersed in 7 ml of Letheen Broth, followed by incubation at 37ºC for 48 h. Microbial growth was evaluated by turbidity of the culture medium. A 0.1 ml inoculum obtained from the Letheen Broth was transferred to 7 ml of BHI, and incubated at 37ºC for 48 h. Bacterial growth was again evaluated by turbidity of the culture medium. Gram stain of BHI cultures was used for verification of contamination and growth was determined by macroscopic and microscopic examination. The best performance of antimicrobial effectiveness of NaOCl was observed in the direct exposure test, and of CHX was observed in the agar diffusion test. The magnitude of antimicrobial effect was influenced by the experimental methods, biological indicators and exposure time.

Operative procedural errors must be well analyzed in order to avoid influence negatively the root canal treatment (RCT) prognosis. The successful RCT prevents tooth loss and avoids pain and apical periodontitis. This review aimed to categorize common operative procedure errors and clinical factors associated with RCT. Based on this, will be approached common errors of procedures within the clinical operative sequence: endodontic treatment planning, pulp and periapical disease diagnosis, anaesthesia, access cavity preparation, isolation with rubber dam, root canal preparation, root canal filling and retreatment, restoration of endodontically treated teeth, postoperative pain, follow up of endodontically treated teeth. The professional must remind that in each phase of RCT an operative error may have adverse implication on prognosis, and these errors characterize risk factors to failure. The knowledge of probable operative procedural errors and its consequences are essentials to avoid future problems to the tooth health.