BACKGROUND:Root canal preparation is a key step in root canal therapy.In recent years,with the rapid development of new nickel-titanium instruments,the results of root canal shaping ability have been significantly improved.However,the shaping abilities of different nickel-titanium instruments are also different.At present,there are few reports about the influence of the shaping ability of R-phase heat treatment NIC X-FILE and DENCO Pre-Shaper in simulated curved canals. OBJECTIVE:To compare the shaping effect of NIC X-FILE and DENCO Pre-Shaper nickel-titanium instruments in preparation for simulated curved canals. METHODS:Fifty simulated resin-curved canals were selected and randomly divided into two groups(n=25).NIC X-FILE and DENCO Pre-Shaper nickel-titanium files were used for root canal preparation.The root canal preparation time was recorded.Images of pre-and post-root canal preparation were taken.Image processing and analysis software were used to measure the amount of resin removed from the inner and outer walls of the root canal at each observation point.Statistical software was used to compare the root canal preparation time and centering ability of two kinds of mechanical nickel-titanium files. RESULTS AND CONCLUSION:(1)The average root canal preparation time was(1.58±0.02)minutes in the DENCO Pre-Shaper group and(2.22±0.03)minutes in the NIC X-FILE group.There was a significant difference between the two groups(P<0.05).(2)The amount of resin removed from the inner walls of the root canal of the DENCO Pre-Shaper group at 4,5,7,8,9,and 10 mm from the apical foramen was higher than that of the NIC X-FILE group(P<0.05).The amount of resin removed from the outer walls of the root canal of the DENCO Pre-Shaper group at 3,5,6,7,and 8 mm from the apical foramen was lower than that of the NIC X-FILE group(P<0.05).(3)At 2,4,5,6,7,8,and 9 mm away from apical foramen,the centering ability of the NIC X-FILE group was better than that of the DENCO Pre-Shaper group(P<0.05),and the centering ability of the NIC X-FILE group was the best at 4 mm away from apical foramen.(4)The results show that DENCO Pre-Shaper has higher mechanical efficiency than NIC X-FILE nickel-titanium root canal files.However,the centering ability of DENCO Pre-Shaper is inferior to NIC X-FILE nickel-titanium root canal files.