1, complete the pulp cavity into the initial preparation: NaOCI must enter the pulp cavity and root canal system before root canal instruments, NaOCl flushing, soaking effect should be throughout the root canal preparation process. 2.When expanding and filing the root canal: a file needle can be dipped in EDTA gel to enter the root canal to accompany the operation, in order to provide lubrication for mechanical preparation. Every time a preparation instrument is replaced, the root canal should be flushed with 2-5 ml NaOCl solution, and the pulp cavity should always be filled with NaOCl to increase the effective action time of chemical disinfection. 3. Apical root canal preparation: Prepare at least to 35 gauge to accommodate the insertion and proximity of a 30 gauge Navi flushing needle to the root tip. 4, Mechanical preparation should be fully rinsed: each root canal should be fully rinsed with a high dose of NaOCl, followed by 5 ml of EDTA solution for 1 min to remove the staining layer. 5.Ultrasonic rinsing: 1~3 min. 6.Final rinsing: NaOCl should be used, with at least 2 ml of rinsing solution for each root canal to thoroughly neutralize the acidity of EDTA and allow NaOCl to penetrate into the open dentin tubules. 7. Final rinsing: 2% CHX can also be used, especially for retreatment cases. Before flushing with CHX, water or 95% ethanol should be used to remove the effect of NaOCl. 8.Before root canal filling: 95% ethanol rinsing with 3 ml per root canal is optional to dry the canal and reduce the surface tension of the canal wall.