ProFile Nickel-titanium Rotary Instruments Research Articles

Effect of Electropolishing ProFile Nickel–Titanium Rotary Instruments on Cyclic Fatigue Resistance, Torsional Resistance, and Cutting Efficiency

This study investigated the effect of electropolishing ProFile nickel titanium rotary instruments on torque resistance, fatigue resistance, and cutting efficiency. Size 25/.04 ProFile files (Dentsply Maillefer, Switzerland) that were nonpolished for the control group ( n = 15) and electropolished for the experimental group ( n = 15) were used for each experiment. Cyclical fatigue was determined by counting rotations until breakage with an applied 30°, 45°, and 60° curve with a 5-mm radius. Torque and angle at failure were measured by rotating clamped files at 2 rpm until breakage. Cutting efficiency was determined by measuring the velocity of file advancement into plastic blocks with 100-g constant force for 5 seconds. Data were analyzed by either an unpaired t test or analysis of variance followed by a Fisher probable least-square difference test. Electropolishing significantly reduced resistance to cyclic fatigue but did not affect torsional resistance. However, electropolishing reduced the angle at failure and amount of unwinding. Electropolishing did not significantly affect cutting efficiency.

Fracture of ProFile nickel–titanium rotary instruments: a laboratory simulation assessment

To determine the incidence of ProFile nickel-titanium rotary instrument fracture in an endodontic laboratory simulation. Three hundred and sixty dental students used 2880 ProFile nickel-titanium rotary instruments to prepare 1440 simulated root canals in 720 plastic teeth, and another 2880 ProFile nickel-titanium rotary instruments to prepare 1440 natural root canals in 720 extracted teeth. A standardized crown-down rotary instrumentation technique was used, which included measures to prevent fracture. Rotary instrument fracture was monitored during and after completion of the laboratory simulation exercises to determine the incidence of fracture. When fracture occurred, data were collected concerning the size of the instrument, the length of the instrument fragment, the location of the fragment in the canal and the curvature of the canal in which the instrument fractured. The incidence of instrument fracture was 0.41% in plastic simulated canals and 0.31% in natural root canals. The overall incidence of instrument fracture was 0.36%. Of the instruments that fractured 67% were size 25, 0.04 taper; and 81% of the fragments were located in the apical third of the canal. The mean, median and mode of the fragment lengths were all 3 mm. The low overall incidence of fracture in this study suggests that ProFile rotary instruments are safe for use by dental students in laboratory simulations and that if preventive measures are taken the incidence of instrument fracture can be minimized.

Failure of ProFile Ni-Ti instruments used by an inexperienced operator under access limitations.

The purpose of this study was to evaluate the failure incidence of ProFile nickel-titanium rotary instruments (PRI) when used by an inexperienced operator in conjunction with different motors and under limitations of access. PRI with 0.06 taper were used by an inexperienced operator in a crown-down technique. The teeth were mounted in resin arches of a phantom head to reproduce limitations of access. In groups 1-4, air, high torque control, low torque control and very low torque control motors were used, respectively. Each group included 30 canals in extracted human molars. One set of PRI sizes 40-15 was used for each canal; the PRI were sterilized before each case. A 2.5% NaOCl solution was used as an irrigant. An inexperienced operator performed all the cleaning and shaping procedures after application of a rubber dam. The opening of the mouth in the phantom head was standardized for the four groups. The number of deformed and separated instruments was recorded for the various experimental groups and analyzed statistically for significance with chi-square tests. A high incidence of instrument deformation and separation occurred with the air, high torque control and low torque control motors. Only seven and two instruments deformed and separated, respectively, with the very low torque control motor, whereas at least 23 and 10 instruments deformed and separated respectively with the other motors. A very low torque control motor was safer than on air, high torque control or low torque control motors when PRI with 0.06 taper were used by an inexperienced operator in a crown-down manner at 170 rpm.

Cyclic Fatigue of Endodontic Nickel Titanium Rotary Instruments: Static and Dynamic Tests

Endodontic instruments upon rotation are subjected to both tensile and compressive stress in curved canals. This stress is localized at the point of curvature. The purpose of this study was to evaluate the cyclic fatigue of 0.04 ProFile nickel titanium rotary instruments operating at different rotational speeds and varied distances of pecking motion in metal blocks that simulated curved canals. A total of 150 ProFile instruments were made to rotate freely in sloped metal blocks at speeds of 200, 300, or 400 rpm by a contra-angle handpiece mounted on an Instron machine. The electric motor and Instron machine were activated until the instruments were broken in two different modes, static and dynamic pecking-motion. The fractured surfaces of separated instruments were examined under a scanning electron microscope. All data obtained were analyzed by a stepwise multiple regression method using a 95% confidence interval. The results demonstrated that the time to failure significantly decreased as the angles of curvature or the rotational speeds increased. However, as pecking distances increased, the time to failure increased. This is because a longer pecking distance gives the instrument a longer time interval before it once again passes through the highest stress area. Microscopic evaluation indicated that ductile fracture was the major cyclic failure mode. To prevent breakage of a NiTi rotary instrument, appropriate rotational speeds and continuous pecking motion in the root canals are recommended.

Failure of ProFile instruments used with air, high torque control, and low torque control motors.

The purpose of this study was to evaluate the influence of 350-rpm rotational speed on the failure incidence of ProFile nickel-titanium rotary instruments (PRI) when used by an experienced operator in conjunction with different motors. Extracted human mandibular and maxillary first and second molars demonstrating curvatures greater than 25 degrees were used. PRI sizes 40 to 15 and with 0.06 taper were used in crown-down fashion at 350 rpm. In groups 1 through 4, air, high torque control, low torque control, and very low torque control motors were used, respectively. Each group included 30 canals. One set of PRI was used for each canal. Before each use the PRI set was sterilized by steam autoclave. The canals were enlarged until a size 25 PRI reached the working length. A 2.5 x magnification was used to check for instrument deformation after each passage. The number of deformed and separated instruments was recorded for the various experimental groups. Instrument deformation and separation did not occur in any of the 4 groups. The results suggested that the use of PRI in conjunction with the different motors by an experienced operator in a crown-down manner at 350 rpm is safe.

Shaping and cleaning the root canal system: A scanning electron microscopic evaluation of a new instrumentation and irrigation technique

The purpose of the present scanning electron microscopic study was to investigate the efficacy of a combination of EDTA, NaOCl, and surface-active irrigating solutions during and after root canal preparation with ProFile nickel-titanium rotary instruments. Thirty canals were divided into three groups, instrumented and irrigated as follows: 5% NaOCl and a final flush with 17% EDTA were used for group A; group B specimens were irrigated using 17% EDTA, followed 15 s later by 1% TRITON X-100 (tensioactive agent) and then by 5% NaOCl; and group C specimens were irrigated with the same combination, but once shaping procedures were completed the irrigating sequence was repeated three times. After scanning electron microscopic evaluation, group C specimens exhibited the most effective debridement of the root canals. Results showed that tensioactive agent contributed to enhanced debridement. Cleaning was significantly improved once shaping procedures were completed.