The Influence of Different Angles and Reciprocation on the Shaping Ability of Two Nickel-Titanium Rotary Root Canal Instruments

Abstract

Purpose: The purpose of the present study was to investigate and compare the effect of different reciprocating movements and angles on the shaping ability of the WaveOne and the single-file ProTaper F2 using cone beam computed tomography (CBCT). Materials and methods:The mesiobuccal canals of 40 extracted maxillary molars, with curvatures of 20 to 45° were coded and randomly divided into 4 equal experimental groups according to the instrument used (ProTaper F2 file and WaveOne) and the reciprocation range, for both instruments, a 150° angle was used for cutting and a 30° angle was used for release. Group 1 -WaveOne primary 150° CCW rotation angle and 30° CW rotation angle; Group 2 -WaveOne 90° CCW rotation angle and 30° CW rotation angle; Group 3 -ProTaper F2 150° CW rotation angle and 30° CCW rotation angle; Group 4 -ProTaper F2 90° CW rotation angle and 30° CCW rotation angle. Canals were scanned before and after preparation using CBCT to evaluate the volumetric change, canal transportation and the canal centering ability at 2.6, 5.2 and 7.8 mm from the apex. The mean ± standard deviation (SD) values were analyzed, and the significance level was set at p ≤ 0.05. Results:There was no significant difference in the amount of dentin removed among the experimental groups, except that WaveOne 150°CCW 30°CW significantly showed the least volume of dentin removed (0.40 ± 0.9) at 7.8 mm. value of root canal transportation in both the mesial and furcal directions and in both the coronal and apical directions compared to the other groups. At the 7.8 level, WaveOne 150°CCW 30°CW yielded the highest mean centering ratio, whereas ProTaper F2 CW 150° CCW 30° yielded the lowest, statistically significant at p ≤ 0.05. Conclusion:The results of the present study demonstrated that differences among various reciprocating motions and angles could affect the shaping ability of a single-file Nickel-titanium (NiTi) instrument.

Classification and cyclic fatigue evaluation of new kinematics for endodontic instruments

“…All of the evaluated combined motions significantly increased the fatigue resistance compared with the CR motion, but they were also significantly different from each other. Accordingly, previous studies have shown that changing the kinematics of the reciprocating motion can significantly affect the fracture resistance of NiTi instruments . The results of our study can be further explained by understanding the effect of each motion on NiTi instruments.…”

“…The NCF is useful for comparing different rotary instruments; however, it is not suitable for comparing the performance of different motions (11). Accordingly, previous studies have shown that changing the kinematics of the reciprocating motion can significantly affect the fracture resistance of NiTi instruments (7,(24)(25)(26)(27)(28)(29)(30). Thus, in the present study, the results were expressed as the time to fracture.…”

“…Changing the angles of the motions affects cyclic fatigue, torsional resistance and performance of the instruments (7,(27)(28)(29)(30)(31)(32)(33)(34). For RR motions, decreasing the angular range for WaveOne instruments increased the fatigue resistance, but also the preparation time (32).…”

“…Instead of directly simulating clinical conditions, cyclic fatigue tests aim to control variables (e.g., curvature angle, position and axial motion) to obtain a fair mechanical comparison between instruments or motions (7,10,11,(29)(30)(31). Instead of directly simulating clinical conditions, cyclic fatigue tests aim to control variables (e.g., curvature angle, position and axial motion) to obtain a fair mechanical comparison between instruments or motions (7,10,11,(29)(30)(31).…”

“…In the present study, the motor, files, and artificial canals used were all standardised to focus on the effects of the type of motion on the cyclic fatigue resistance of the instruments. Thus, the observed differences can be only attributed to the different motions and their angles .…”