Treatment: Once the working length is lost, it should be treated accordingly according to different reasons. When root canal preparation is performed by the step-back method, the working length is determined before preparation, and a small part of the working length will be lost after preparation due to the full expansion of the root canal crown 2/3 and the moderate straightening of the bend; for the medium and heavy bent root canals, the working length should be redetermined for every 3 expansions during root canal preparation to avoid excessive root canal preparation.
2.root canal blockage: When the root canal file cannot enter the full length of the root canal and reach the apical narrowing, it is called root canal blockage. There are many reasons for root canal blockage. It mainly includes the accumulation of dentin debris and tissue debris in the apical area, blockage of filling materials, cotton twist, paper twist, fractured instruments and adhesive blockage, etc.
Treatment: In order to avoid the occurrence of root canal blockage, it is better to follow the following prevention principles: before opening the pulp, make sure to remove the carious tissue, no base enamel and loose filling, etc.; the pulp hole preparation should be fully expanded, especially when there is a full crown present.