Abstract: PURPOSE: To explore the application value of three reciprocating single nickel-titanium instruments in preparation of simulated curved root canals. METHODS: One hundred and fifteen single-curved resin simulation root canals were selected and divided into Reciproc group (group A, 28), One file group (group B, 29), Wave One group (group C, 29) and control group (group D, 29) by random graph method. The simulated root canals were prepared according to the specifications of the instructions, root canal preparation, resin removal, root canal cleaning effect, center positioning ability and root canal width were compared. SPSS 22.0 software package was used for statistical analysis. RESULTS: There was no significant difference in quality and curvature among four groups(P>0.05). The difference in root canal preparation time among the four groups was statistically significant (P<0.05), and the root canal preparation time in group B was the shortest(P<0.05). Comparison of resin removal at the root canal orifice and the midpoint of the bending start point among four groups, the difference was statistically significant(P<0.05). The root canal wall debris scores and smear layer scores in four groups were significantly different(P<0.05). Compared with group A, B and D, the root canal wall debris scores of the crown, middle and tip of group C were the lowest, the scores of smear layer on the crown and middle of the root canal wall was the lowest(P<0.05). There was no significant difference in the center positioning ability of the four groups at 5 mm, 6 mm and 7 mm from the apical foramen(P>0.05). There was no significant difference in root canal width among four groups (P>0.05). CONCLUSIONS: Reciproc, One file and Wave One reciprocating single nickel-titanium instruments can maintain the original shape of the simulated root canal. Compared with Reciproc and Wave One, One file has better root canal shaping ability and cleaning effect.

Key words: Reciprocating rotation, Single file, Cutting ability, Forming ability