Evaluation of preparation times of WaveOne Gold reciprocating instruments compared to two analogous counterparts

and 5 mL 3% sodium hypochlorite was used as irrigation solution. Mean and standard deviations were determined for each group, and analysis of variance was used to statistically compare the mean glide path preparation times for the three groups. The fastest final canal preparation time was achieved by WOGG/PWOG (41.78 ± 10.58s), followed by OFGP/ POFS (42.02 ± 12.16 s) and then EGP/PEOF (42.49 ± 10.44s). There were no statistically significant differences between the canal preparation times of the three combination groups (p>0.05). Thermomechanical processes have resulted in the development of nickel-titanium (NiTi) endodontic glide path and shaping files with increased flexibility and fatigue resistance compared to their predecessors. Companies

Evaluation of preparation times of WaveOne Gold reciprocating instruments compared to two analogous counterparts are now developing analogous instrumentation systems that are similar in form and function to their competitors' but are constructed from differing proprietary heat-treated NiTi.
The preparation of a glide path prior to the introduction of rotary NiTi instruments is a standard adjunct to ensure more safety during root canal instrumentation. 1 A glide path can be defined as a smooth, radicular tunnel from the canal orifice to the physiologic terminus of the root canal. 2 Varela-Patinǒ et al. 3 found that fewer instrument fractures occurred when a wide and smooth-walled glide path was created and the canal was pre-flared before canal preparation with rotary files. 3 Glide path preparation allows for an understanding and appreciation of the original canal anatomy, renders the canal patent to receive rotary files, and permits a more effective and safer action during root canal shaping. 4,5 Once established, successful glide path preparation can reduce torsional stresses and increase the life span of a rotary instrument by up to 6 times. 5 A study by Patiño et al., 3 showed that the incidence of instrument separation was significantly reduced in canals in which preparation was preceded by proper glide path preparation. A separate study showed a higher incidence of distortion and separation of NiTi files in the absence of initial glide path preparation. 6 NiTi rotary PathFiles (Dentsply Sirona, Ballaigues, Switzerland) were introduced in 2009 to facilitate glide path preparation. A study by Cantatore et al., 7 showed that Path-Files can prepare a glide path with fewer irregularities and better conservation of original canal anatomy, even after canal preparation by inexperienced users. In recent years, single-file rotary and reciprocating glide path preparation systems have been introduced.
The use of NiTi shaping files in a reciprocating motion is a recent innovation, with manufacturers claiming increased resistance to instrument separation compared to rotary instrumentation, and to adequately shape and preserve the anatomy of root canal systems. 8 Although some studies indicate more debris accumulation with the reciprocating technique, 9 compared to multiple consecutive rotary files, overall cleaning effectiveness has been shown to be equal or comparable 10,11 and, in some, better 12 than traditional rotary systems.
Several studies have also shown that the reduction of the bacterial load was found to be similar in both reciprocating and rotary systems. [13][14][15] In a review article by Plotino et al., 8 they conclude that reciprocating files have a lower incidence of dentinal defects and cracks. However, a study by Deus et al., 16 observed no association between these cracks and shaping with single-file reciprocating or multi-file rotary systems.
The aim of this ex vivo study was to compare the total glide path and canal preparation times of WaveOne Gold Glider (Dentsply Sirona) combined with the Primary Wave-One Gold (Dentsply Sirona), Edge GlidePath (EdgeEndo, Albuquerque, New Mexico, USA) followed by the Primary EdgeOne Fire (EdgeEndo); and One File G Glide Path (PacDent, Brea, CA, USA) file combined with the Primary One File G (Pac-Dent) Shaping file. The null hypothesis tested was that there are no differences in canal preparation times between the three groups. Currently, there are no published studies comparing the total canal preparation times of these analogous shaping systems in curved canals of mandibular molars.
Extracted mandibular first molar teeth with curved mesial roots containing two separate canals and mesial apical foramina were collected for this study. Radiographs (Carestream Health Inc., NY State, USA) were used to select a total of 60 previously untreated mesiobuccal canals with closed apices and curvatures of 25° to 35° according to the Schneider method. 17 The 60 specimens were engraved from 1 to 60 and then randomly divided into three experimental instrumentation groups of 20 each using an online randomiser tool (Research Randomizer version 4.0) (Urbaniak & Pious 2011). 18 All specimens were mounted in an FKG vice (FKG Dentaire, La Chaux-de-Fonds, Switzerland) designed for endo training, to simulate clinical situations and standardise preparation conditions. After access cavity preparation, working length (WL) was determined by deducting 0.5 mm from the length of the canal measured to the major apical terminus under 10 times magnification using a surgical microscope (Zumax Medical Co. Ltd, Suzhou, China).
The mesio-buccal canals were located and explored with a size 08 Senseus K-Flexofile (Dentsply Sirona) and canals were negotiated to patency. An initial manually reproducible micro-glide path was prepared by negotiating a size 08 Senseus K-Flexofile to WL with increasing amplitudes of 1-3 mm. This process was repeated using a pre-curved size 10 Senseus K-Flexofile (Dentsply Sirona). Reproducibility was checked by the ability to place the Senseus K-Flexofile 3-4 mm short of working length and pushing it to full working length without any obstruction by means of light finger pressure.
Glide path preparation and root canal shaping were carried out by the same operator and new files were used for each tooth. RC Prep (Premier, Pennsylvania, USA) was used as a lubricating agent during the glide path enlargement and 3.5% sodium hypochlorite was used for canal irrigation after the use of each file. Patency was maintained throughout the glide path and root canal preparations with an ISO size 08 Senseus K-Flexofile.
The X-Smart IQ endodontic motor (Dentsply Sirona) was used in reciprocation mode for both glide path preparation with the Wave One Gold Glider (WOGG), and shaping with the Primary Wave One Gold (PWOG). This was done on the WaveOne Gold setting according to the manufacturer's instructions.

Specimen preparation
Glide path preparation and root canal shaping The X-Smart IQ endodontic motor (Dentsply Sirona) was used in reciprocation mode for both glide path preparation with the One File G Glide Path file (OFGP), and shaping with the Primary One File G Shaping file (POFS). This was done on the WaveOne Gold setting according to the manufacturer's instructions.
The X-Smart IQ endodontic motor (Dentsply Sirona) was used in rotary mode (300rpm, 3Ncm -ProGlider settings) for glide path preparation with the Edge GlidePath (EGP), and shaping with the Primary Edge One Fire (PEOF) in reciprocation. This was done on the WaveOne Gold setting according to the manufacturer's instructions.
Each glide path or root canal preparation file was only used to prepare one canal before being discarded. The total time taken to prepare a glide path and to complete the root canal preparation of each canal was recorded (in seconds) by means of an iPhone stopwatch (Apple Inc., Cupertino, California). The time taken to change files was not recorded. Throughout the instrumentation process, RC Prep was used as a lubricant, and 5 ml 3% sodium hypochlorite was used as irrigation solution.
Mean and standard deviations were determined for each group, and analysis of variance was used to statistically compare the mean glide path preparation times for the three groups. There were no statistically significant differences between the canal preparation times of the three combination groups (p> 0.05).
The total canal preparation time for three glide path preparation instruments and their associated shaping systems were investigated in mesio-buccal root canals of mandibular molars with moderate canal curvatures of between 25° and 35°.
Each instrument was used in a reciprocating motion except for the EGP, which was used in continuous rotation before final shaping with the Primary EOF. Recently Edge-Endo launched its reciprocating glide path file, EdgeOne Fire GlidePath, which was not available at the time this research was undertaken.
The WaveOne Gold Glider (Dentsply Sirona) is a single glide path file with an ISO 15 tip size, variable taper from 2% at D0 to 6% at D16, a parallelogram-shaped crosssection, and a semi-active tip. WaveOne Gold (Dentsply Sirona) is a shaping system characterized by an alternating offset parallelogram-shaped cross-section design with two 85° cutting edges. Both these systems are manufactured from Gold-Wire and are used in reciprocation.
The Edge GlidePath file (EdgeEndo) is a variable tapered single rotary glide path file with an ISO 19 tip size, a triangular cross-section, non-cutting tip, and a progressive taper with a 15mm cutting length. EdgeOne Fire (Edge-Endo) is a reciprocating shaping system similar to Wave-One Gold. Both the EdgeOne Fire and Edge GlidePath systems are manufactured from a new proprietary heattreated NiTi referred to as "FireWire". 19 The One File G Reciprocating File System (Pac-Dent) consists of a single glide path file and four shaping files.
The One File G Glide Path file (Pac-Dent) has an ISO 15 tip, 2% taper, and a parallelogram-shaped cross-section. One File G Shaping files (Pac-Dent) each have a parallelogram-shaped cross-section, constant helical angle of 24° along the active length of the instrument and two 80° cutting edges and are used with the same handpiece settings as WaveOne Gold. The One File G Glide Pathand Shaping files are made using proprietary heat-treated NiTi wire and have roundly tapered guide tips without any cutting edges.
In the present study the total time taken to prepare a glide path and shape each canal was recorded (in seconds). There were no statistically significant differences in preparation times between the three combination groups in this study.
Several studies have compared single and multiple instruments in curved canals and have concluded that single file systems are significantly faster. 12,20,21 In a study by Vorster et al., 22 glide path preparation times of WOGG in a reciprocation motion were compared to that of K-Files and PathFiles in a rotary motion. WOGG showed statistically significantly faster glide path preparation times compared with both the K-file and the PathFile preparation groups. The authors attributed the results to the multiple instrument use in each of the other two groups compared to the WOGG group, which consisted of a single instrument.

Data collection
Statistical analysis Some of the studies examining preparation times favour reciprocation, 23 while others claim that single files used in rotation are faster. 24 A study examined the shaping ability and preparation times of different single-file NiTi systems in rotation and reciprocation. 25 In this study by Hwang et al., 25 single Mtwo (VDW, Munich, Germany) and Reciproc (VDW) shaping files were used after glide path preparation with a size 15 K-File and no differences in preparation times were found between the shaping groups. A separate study examined the shaping ability of different NiTi systems in simulated S-shaped canals with and without glide path preparation, and concluded that glide path preparation exerted no significant effect on preparation times of these canals. 26 In a study by D'Amario et al., 27 they compared the canal preparation time of One Shape (MicroMega, Besancon, France), Reciproc and WaveOne preparation systems after glide path preparation with a size 10 K-File. They found no clinically relevant differences in preparation times between the three single file systems. Their recorded times were much higher than that of the current study. This could be attributed to the curvature of their tested specimens or the fact that the present study incorporated glide path files, which decreased the total shaping times.

DISCUSSION
In this study, preparation times were similar for all three combination groups. These single-file glide path and shaping systems are appealing for use in the clinical setting because of their reduced overall canal shaping time, potential low cost, prevention of cross-contamination, and easy clinical application.
Within the limitations of this study, it can be concluded that all three groups presented with similar preparation times, and no statistically significant differences were noted (p> 0.05).
The limited information on EdgeEndo and One File G systems in the literature made it impossible to compare the results obtained in this study with other studies. To date, no paper has been published on the preparation times of these file combinations. It is however recommended that further studies are needed to evaluate these endodontic glide path and shaping systems clinically.