Major clinical findings of endodontic retreatment: a concise systematic review

Introduction: In the endodontic treatment and retreatment scenario, the primary objective is to eliminate necrotic tissue and infectious bacteria, especially cleaning and shaping. Endodontic retraction is a procedure performed on a tooth that has received a previous attempt at a definitive treatment that has resulted in a condition that requires further endodontic treatment to achieve a successful outcome. The main cause of treatment failure is insufficient cleaning and inadequate filling. Objective: The present study carried out a concise systematic review to evaluate the main findings of clinical studies on endodontic retreatments, showing the main techniques, efficacy, and safety. Methods: The rules of the Systematic Review-PRISMA Platform. The research was carried out from December 2021 to March 2022 and developed based on Scopus, PubMed, Science Direct, Scielo, and Google Scholar. The quality of the studies was based on the GRADE instrument and the risk of bias was analyzed according to the Cochrane instrument. Results: A total of 124 articles were found. A total of 74 articles were evaluated in full and 17 were included and evaluated in the present study. Studies have demonstrated the effectiveness of rotational systems in endodontic retreatment but never producing completely obturator-free root canals. Reciproc instruments were associated with significantly higher cyclic fatigue strength than WaveOne instruments. The persistent infection microbiota is polymicrobial with a predominance of E. faecalis and P. gingivalis in all stages of endodontic retreatment, regardless of the method used for microbial identification. A higher bacterial load and lower lipoteichoic acid level were found in the 2-visit group after the retreatment protocol. Postoperative pain was significantly reduced at 48 and 72 hours after the application of nano-silver and nano-calcium hydroxide alone. Conclusion: The results of clinical trials showed that the root canal instrumentation system with rotary files maintains the quality of the root preparation and reduces the number of files needed to obtain a canal, which would consequently reduce the operative time and also considerably reduce the risk of torsion fracture within the root canal, allowing successful endodontic retreatment. Also, a condition for successful endodontic retreatment is the adequate cleaning of the root canals, therefore, special attention must be given to the technique used to remove the filling material