Shaping ability of two rotary instruments in simulated canals: stainless steel ENDOflash and nickel‐titanium HERO Shaper

Abstract

To compare the shaping ability of two rotary instruments in simulated curved canals: stainless steel ENDOflash Files (KaVo, Biberach, Germany) and the recently introduced nickel-titanium HERO Shaper instruments (Micro-Mega, Besançon, France). Simulated root canals with 35 degree curves in resin blocks were prepared to size 30, .04 taper (HERO Shaper) using a crowndown technique or size 30, .02 taper (ENDOflash) using a rotary motion and a rotation speed of 400 or 250 rpm respectively. In both groups, irrigation was performed with 1 mL distilled water after each instrument size and Glyde (Dentsply Maillefer, Ballaigues, Switzerland) were used. Canals (n = 17 per group) were scanned before, during and after preparation. The assessment of preparation shape was carried out with a computer image analysis program. Material removal was measured at seven points beginning 1 mm from the end-point of the canal. Statistical analysis was performed using Wilcoxon's test and Fisher's exact test (P < 0.05). No instrument fractures, apical blockage or loss of working length (WL) occurred. More zips (10 vs. 4) and more strippings (17 vs. 0) were created with ENDOflash compared with the HERO Shaper. There were significant differences in terms of the amount of resin removed on the inner wall of the curvature obtained with the two instruments (P < 0.0001). On average, HERO Shaper instruments removed material more evenly on the outer and inner wall of the curvature. Considering the different points of measurement, there were significant differences between the two systems both on the inner and outer walls at WL-1, 2, 5 and 6 mm (P < 0.05). The HERO Shaper had a more centred enlargement compared with the ENDOflash. Stainless steel rotary ENDOflash instruments did not perform as well as HERO Shaper instruments and created an increased risk of root canal transportation. Nickel-titanium rotary HERO Shaper instruments maintained the original curvature significantly better.