Abstract: Objective To evaluate the ability to keep the original root canal anatomy flow by Reciproc single file in preparing molar curved root canals. Methods Patients aged from 18 to 59 years old who were newly diagnosed with pulp disease were selected. According to Schneider measurement, 100 first molar curved root canals (20°～30°) and 200 canals (cheek, tongue curved root canals) were randomly divided into Reciproc group of 50 cases with 100 canals, and Protaper group of 50 cases with 100 canals. Then root canals were prepared, followed by the measurement of root canal curvature of the dental film chip in first root canal file, the final root canal file, and the trial point root canal file. The apical transportation of root canals in two groups were compared, and the effects of root canal formation as well as root tip closure were evaluated. Results Success rate in Reciproc group was 99%, while success rate in Protaper group was 92%, and the difference was significant (P<0.05). Conclusion With its innovative design, the Reciproc single file enables the preparation molar curved root canals to have fine formation, light reaction, good closure in the apex, quickness and high efficiency, making a single file take place of a set of files.

Key words: reciprocating movement, root canal preparation, Reciproc, apical transportation