Biomechanical techniques used in preparing root canals emerged from manual preparations to rotary techniques utilizing nickel–titanium instruments. The use of NiTi rotary files for preparing root canals enabled the creation of consistently tapered preparations more predictably and efficiently, while lessening procedural mishaps, especially in curved canals (Bryant et al. 1998).
Due to continuing search of affordable priced files having good properties, E3 Azure and Fanta AF one file systems which are manufactured using recent innovations to increase files performances (blue heat treatment) and as claimed by the manufacturer can also be used in both rotation and reciprocation motions, were chosen in this study to assess their cutting efficiency.
Simulated resin canals were used for standardizing the study groups. Despite their deficiency of the innate varying hardness, content of water, and the created smear layer when instrumenting which makes them not seem as the best replacement for dentin (Shen and Haapasalo 2008), resin blocks show consistent performance and a great degree of reproducibility as regards to hardness, dimensional stability, fixed curvature, angle, and diameter. Hence, the use of simulated canals sidestepped the variations in morphology and dimensions of canals of extracted human teeth (Al-Omari et al. 1992).
The heat treatment technology used for manufacturing the new rotary systems increased their flexibility and fracture resistance (Mittal et al. 2017).
A limited number of studies were conducted on these novel rotary files to assess the effect of these properties on cutting efficiency. This is mostly due to the discrepancy in the criteria of assessment. To our awareness, this is the first study that assesses and compares cutting efficiency of Azure and Fanta AF one file systems.
E3 Azure manufacturer claims that it can be used for the common motions used; rotation, reciprocation and optimum torque reverse.
The heat treatment grants the Azure files their transforming ability from martensite to austenite at body temperature. This technology also permits curving of the file prior to introduction in the canals, allowing them to proceed with ease in curved canals, with decreased liability of ledges and perforations occurrence. The adjusted S-shape cross section of the file decreases its core, granting it flexibility and giving more space for superior removal of debris.
The AF F One, a NiTi Rotary file manufactured to be used in continued rotation has two active cutting tips and a flat side-cut, providing it with better cutting efficiency, as debris are easily cleared up from the flutes to the safe-sided relief area through vertical blades, then out of the canal. Furthermore, the flat side-cut lowers the contact area with canal walls, providing more room for irrigants during preparation and minimizing stresses acting on the file, thus lessening the chances of file disengagement.
In order to lessen the preparation time, recommendations have been made to use a single file in different kinematics for the preparation of the entire canal (Yared 2008). Single file systems are looked at as a breakthrough to a less complicated path, in comparison to multiple file systems (Mittal et al. 2017), by minimizing the cost and clinician’s operating time.
For this work, one file was chosen for each system; 25/06, the manufacturers recommended a working speed of 350 rpm and a torque of 2.5 Ncm. Single file systems introduced today can work in both continued rotation or reciprocating motions (Kumar and Gade 2015). The same operator prepared all the canals; thus, the operator was not a variable (Zhao et al. 2013).
Several methods have been advocated to measure the cutting efficiency; weight loss, (Yguelhenry et al. 1990; Haikel et al. 1996). Post-instrumentation induced debris (Wan et al. 2010) maximum depth of penetration inside the canal (Schafer and Oitzinger 2008a) preparation time (Schafer et al. 2006a; Burklein et al. 2013) and cutting depth in resin blocks (Rubini et al. 2014).
From the varying methods of evaluation, weight loss method provides the utmost reliable quantitative measurement (Chi et al. 2016).
Results of this study demonstrated that samples instrumented with Fanta AF One rotary system showed significantly higher weight loss than Azure rotary system in both rotation and reciprocation (P < 0.001). The two file systems did not show significant difference with rotation and reciprocation motions.
Prior research showed that S-shaped files with 2 sharp cutting edges (which are the cross-sectional designs of the two files used in this study) are accompanied with better cutting efficiency (Burklein et al. 2013; Rubini et al. 2014; Chi et al. 2016; Schafer and Oitzinger 2008b).
Fanta AF One rotary system displayed the greatest cutting efficiency. This may be due to their distinctive positive cutting angles and the unique geometric design. The flat side-cut contributes to a small cross section, creating greater space between canal walls and the file, which allows for more debris collection and removal capability (Schafer et al. 2006b). This ability to remove debris also adds to the efficiency of mechanical instruments, because the removal of cut dentin chips reduces clogging of the cutting blades (Bergmans et al. 2001; Schafer 1999). This feature kept the flutes unclogged and always ready for more dentin cutting.
Neither Rotation nor reciprocation had an impact on cutting efficiency with both files, the reason behind this may be because each file has a feature in the geometric design that prevented the file screw in and allowed for debris clearance causing the file to remove dentin in both motions.
