Abstract: Objective: To compare the efficiency of root canal removal with three simulated treatments of D-RaCe, ProTaper, and Mtwo via simulated root canal. Methods:There are 30 transparent resin root canals were randomly selected and divided into 3 groups. D-RaCe, ProTaper, and Mtwo were used to remove the root fillings. The operation time was recorded, and the images after removal of the root fillings were collected. Image analysis software was used to calculate the residuals. Area, compare the overall clearance rate of the three species. The apical part was divided into three sections from 0-2mm, 2-4mm, and 4-6mm from the apical foramen. The residual area was calculated and the best clearance rate among the three retreatment groups was compared. Result: The shortest operating time for D-RaCe. All samples had residual fillings in the root canal, and there was no significant difference in overall clearance between ProTaper and Mtwo (p>0.05), and all were superior to those in D-RaCe group (p<0.05). In the 0-2mm and 2-4mm sections of the apical foramen, the clearance rate in the D-RaCe group was the lowest, and there was no statistical difference in the 4-6mm sections (p>0.05). Conclusion: The D-RaCeTM has a short operating time, higher fatigue resistance and anti-break ability. ProTaper and Mtwo re-treatments were able to remove most of the root fillings. The clearance rate in the 0-2mm and 2-4mm sections from the apical foramina was better than that in the D-RaCe group.

Key words: Nickel titanium instrument, Resin simulated root canals, Retreatment, Curved root canal