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.

No abstract

Leoni GB, Versiani MA, Silva-Sousa YT, Bruniera JFB, P ecora JD, Sousa-Neto MD. Ex vivo evaluation of four final irrigation protocols on the removal of hard-tissue debris from the mesial root canal system of mandibular first molars. International Endodontic Journal.Aim To evaluate the efficacy of four final irrigation protocols on the reduction of hard-tissue debris accumulated within the mesial root canal system of mandibular first molars using micro-CT analysis. Methodology Forty mesial roots of mandibular molars with a single and continuous isthmus connecting the mesiobuccal and mesiolingual canals (Vertucci's Type I configuration) were selected and scanned at a resolution of 8.6 lm. Canals were enlarged sequentially using WaveOne Small and Primary instruments activated in reciprocating motion without intracanal irrigation to allow debris to accumulate within the mesial root canal system. Then, specimens were anatomically matched and distributed into four groups (n = 10), according to the final irrigation protocol: apical positive pressure (APP), passive ultrasonic irrigation (PUI), Self-adjusting File (SAF) and XP-endo Finisher (XPF). The final irrigation procedures were performed over 2 min using a total of 5.5 mL of 2.5% NaOCl per canal. Reconstructed data sets were coregistered, and the mean percentage reduction of accumulated hard-tissue debris after the final irrigation procedures was compared statistically between groups using the ANOVA post hoc Tukey test with a significance level set at 5%. Results Reduction of accumulated hard-tissue debris was observed in all groups after the final irrigation protocol. Overall, PUI and XPF groups had higher mean percentage reductions of accumulated hard-tissue debris (94.1% and 89.7%, respectively) than APP and SAF groups (45.7% and 41.3%, respectively) (P < 0.05). No significant differences were found when comparing the results of PUI and XPF groups (P > 0.05) or APP and SAF groups (P > 0.05). Conclusions The PUI technique and XP-endo Finisher instrument were associated with significantly lower levels of AHTD compared with conventional irrigation and the modified SAF system protocol in mesial root canals of mandibular molars.

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.