This paper aim the retreatment of root canal and various stages and techniques involved in the retreatment process. The primary reason for the failure of root canal treatment is insufficient disinfection. When primary root canal treatment fails, periapical lesions can be retreated either surgically or non-surgically. Root canal retreatment is a non-surgical procedure that involves the removal of root canal filling materials from the tooth, followed by cleaning, shaping, and filling the canals. The strategic importance of the tooth and its value for treatment should be decided. The success rate is higher in teeth with short root fillings and intact anatomy. Retreatment is based on the principles of primary root canal treatment, such as accurate diagnosis, cleaning, disinfection, filling, and restoration, but it differs in teeth with vital or necrotic pulp. An accurate pre-operative diagnosis is essential to foresee problems that may be encountered during retreatment. This includes the type of root filling, canal anatomy, curvatures, and previously undetected root canals. These factors need to be considered when re-entering the root canal system. During retreatment, infected root canals can be contaminated with bacteria and sometimes fungi or viruses. These infections are often associated with biofilm. The microbial diversity of the filling material and canal system can affect treatment success. The cleaning and disinfection process is crucial. The root canal system must be thoroughly cleaned, and all canals must be determined. Before removing the root filling, coronal canal shaping and cleaning should be performed. During retreatment, it is quite challenging to completely remove the filling material. The filling material in the root canal should be removed mechanically and, if necessary, with solvents. Irrigation is critical for cleaning and disinfecting the canal during the retreatment process. Chelating solutions like EDTA or citric acid can help clean the canal walls. Sodium hypochlorite (NaOCl) is the preferred irrigant and its effectiveness can be enhanced with ultrasonic activation. During retreatment, sodium hypochlorite (NaOCl) is commonly used for disinfecting the root canal. The retreatment of the root canal filling can be successfully carried out with proper techniques and effective disinfection. Although retreatment is generally more challenging, successful outcomes can be achieved with proper treatment planning and preparation.