For an endodontic file to provide good canal shaping, it is essential that it possesses a centering ability inside the root canal (Alshahrani and Al-Omari 2019) and because there is a continuous search for files with reasonable prices, recent innovations (blue heat treatment) and good mechanical properties, this work aimed at assessing the mechanical shaping ability of heat treated E3 Azure and Fanta AF one file systems in both rotation and reciprocation motions.
For standardization of groups, simulated resin canals were favored than natural teeth. Although they are short of inherent variations in hardness, water content, and smear layer formed at time of instrumentation making them not look as an ideal dentin replacement (Shen and Haapasalo 2008), these resin canals perform consistently in terms of hardness and dimensional stability, they permit high degree of reproducibility besides fixed curvature, angle, and diameter. Therefore, using simulated canals bypassed the differences seen in canal dimensions and morphology of extracted human teeth (Al-Omari et al. 1992).
Different approaches are being advocated to evaluate the final shape of the root canal after mechanical preparation. These comprise using stereomicroscope for analyzing, serial sectioning technique (Bramante et al. 1987), microcomputed tomography (Deepak et al. 2015), and radiographic imaging (Bramante et al. 1987). Nonetheless, these techniques without exception have their own advantages and disadvantages. Sectioning of the teeth is sophisticated, invasive, and can lead to loss of material. Microcomputed tomography is not cost‐effective as it only assesses volumetric changes, and possible geometric changes are not analyzed (Ounsi et al. 2011). Alternatively, imaging technique using Adobe Photoshop program, which is the evaluation method adopted in this study, precisely specifies the outlines of the preoperative and the postoperative canals. So, by measuring the variations in width between the pre‐ and postoperative images, it became achievable to compute the extent of resin material removed. Also, incorporating colored inks in pre‐ and postoperative imaging allowed heightened accuracy in canal width measurement without destructing the samples (Alshahrani and Al-Omari 2019).
Newly manufactured thermo-mechanically treated alloy rotary systems added special characteristics of flexibility and fatigue resistance to the files (Taha et al. 2013). Nonetheless, a small number of studies were done to evaluate the effect of these properties on shaping ability of the novel rotary files mainly due to the variation in assessment criteria. To our knowledge, this is the first study that evaluated and compared the shaping abilities of Azure files system with the Fanta AF one files system.
As claimed by the manufacturer, E3 Azure was manufactured for the three familiar types of preparation, to attain a perfect canal preparation; rotation, reciprocation and complex motions (OTR).
The Azure heat treatment technology grants it the ability for transform from martensite to austenite at body temperature. This treatment allows the pre-bending of files before their insertion inside the canal. This enables the files to easily follow the most curved canals, with little risk of perforations and ledges. This file’s cross section is modified S-shape, decreasing the core of the file thus allowing for better debris removal and greater flexibility.
The AF F One Rotary file is also a novel NiTi instrument designed for use in continuous rotation motion. It has two active cutting points and a flat side-cut cross-sectional design. This gives the file a higher cutting efficiency, where debris can be swept from flutes to the safe-side relief area through vertical blades, and then outside the canal. This design also provides a more efficient cutting and less stress on the file, minimizing the possibility of file separation. Moreover, the flat side-cut provides more room for irrigating solutions during instrumentation and a lower surface area contact with canal walls, which decreases the stresses falling on the file. This flat side-cut design is not deeply cut in the file, thus increasing the file’s flexibility without compromising file’s strength. AF F-One file has non-cutting tip, which decreases the likelihood of iatrogenic complications like perforation, zipping, ledges, and canal transportation.
For the sake of minimizing the working time, it has been recommended to use one file with different motions to prepare the whole canal (Yared 2008). Single file systems are considered a progression towards a simpler approach, when compared to systems using multiple files (Mittal et al. 2017), as they save operator’s time, cost and minimize the chances of cross contamination between patients. In this study a single file was used from each system; file 25/06 at 350 rpm speed and 2.5 Ncm Torque as recommended by the manufacturers. Single file systems could be used in either continuous rotation or reciprocation motions (Kumar and Gade 2015).
The root canal preparations were performed by the same operator. Thus, the operator was not a variable (Zhao et al. 2013).
Canal transportation and centering ability are dependable methods to assess if a shaping procedure can sustain the original canal anatomy (Merrett et al. 2006). Therefore, in the current work canal transportation had been assessed as the variation in the amount of resin removed from the canals (Andrade-Junior et al. 2017) at three different positions: 1 (apical), 4 (middle) and 7 (coronal) mm from the apex. File system that produced less transportation of canal curvature in these defined positions was considered to have better shaping ability and better perseveration of the original canal anatomy (Taha et al. 2013).
Results showed no significant difference between files when compared in rotation movement and when compared in reciprocation.
However, the cervical level in both rotation and reciprocation for both files showed a significantly high transportation, this could be referred to the large taper used (0.06) which also leads to less file decreased flexibility leading to more transportation (Saberi et al. 2018).
Wu et al. (2000) claimed that transportation over 0.3 mm apically has a bad impact on the sealing capability of root filling materials. In this study, there wasn’t any transportation over 0.3 mm in any of the groups, however, rotation motion with both instruments showed greater apical transportation than when the files were worked in reciprocation. These results coincide with the results of Berutti et al. (2012a), who stated that the reciprocation permits for a more centered preparation compared to continuous rotation, specifically in the apical third.
When comparing motions, reciprocation showed significantly lower transportation levels in both files. Other studies that used resin blocks to evaluate the shaping abilities of NiTi systems and the amounts of transportation caused by them have announced that reciprocating movements produced more centered preparations than continuous rotation movements (Franco et al. 2011; Berutti et al. 2012b). Cimilli and Kartal (2005) showed that the center of the preparation shifts in a clockwise direction with continuous rotation, but in reciprocation this shift is reduced.
Since engine-based root canal treatment is a valued time relief for patients and practitioners (Schäfer and Lohmann 2002). The mean time for canal preparation was, hence, noted in our work. Results showed that Reciprocation in both groups recorded significantly longer time for preparation than rotation (P < 0.001). This difference could be due to the number of total rotations done by the instrument during shaping; instruments undergo a 360° turn for every cycle in the continuous movement, whereas they undergo a 20° turn with the reciprocating movement in the same time span (Franco et al. 2011).
