Comparison of Shaping Ability of 10 Rotary and Reciprocating Systems: an In Vitro Study with AutoCad.

OBJECTIVE: The aim of this study was to compare the cutting are, root canal anatomy preservation and non-instrumented areas of F360®, F6-SkyTaper®, Hyflex-EDM®, iRACE®, Neoniti®, O.Shape®, P.Next®, Reciproc®, Revo-S® and Wave-One-Gold® size 25 files.
MATERIALS AND METHODS: 300 teeth with a single straight root and a circular or elliptical root canal were divided into 10 groups (1-F360®, 2- F6-SkyTaper®, 3-Hyflex-EDM®, 4-iRACE®, 5-Neoniti®, 6-O.Shape®, 7-P.Next®, 8-Reciproc®, 9-Revo-S® and 10-Wave-One-Gold®) cut into 3 cross sections using an ultrafine cutting disc. They were photographed under a stereo microscope and preinstrumentation analyses were made before rebuilding the teeth with# 10 K- File and epoxy glue. A glide path was created with #10 and #15 K files and each group was instrumented using rotary or reciprocating systems. Cutting areas, root canal anatomy preservation and non-instrumented areas were analyzed using the AutoCAD 2015 Levene's test, the Welch´s test, and the Games-Howell´s test. The Pearson's chi-squared test was used for statistical analysis.
RESULTS: Levene's test showed no equality of variances (P<0.05), therefore Welch´s and Games-Howell's tests were applied to cutting areas, showing significant differences in all thirds and overall (P<0.05). No differences in root canal anatomy preservation were observed (P>0.05). In non-instrumented areas, significant differences were found (P<0.05) in middle third being better in Reciproc®, Neoniti® and WaveOneGold®, and in apical thirds being higher P.Next®, Reciproc®, HyflexEDM®, Neoniti® and WaveOneGold®.
CONCLUSIONS: In cutting area, P.Next® and Reciproc® were superior in coronal third, Neoniti® and Hyflex EDM® medially and apically and Neoniti® and Reciproc® overall. Regarding the root canal anatomy preservation, all systems were similar. For non-instrumented areas, all systems achieved similar results coronally, but Reciproc®, Neoniti® and Wave One Gold® were superior in middle third and P.Next®, Reciproc®, Hyflex EDM®, Neoniti® and Wave One Gold® were superior in apically.

Introduction

Biomechanical preparation is one of the most important procedures in endodontic treatment, influencing irrigation and root canal filling (). It is important to preserve the anatomy in order to reduce damage to dental structures when contaminated dentin is removed and the root canals are formed (). Ideally, root canal shaping should create a continuous tapered preparation from crown to apex while maintaining the original path of the canal and keeping the foramen size as small as is practical (). However, root canal instrumentation can produce apical transportation (), changes in the shape of the root canal () and even perforations ().

In recent years, clinicians have used different rotary and reciprocating systems that differ in symmetry, cross-section, number of uses, alloy, etc. Currently, a new generation of endodontic systems made from nickel-titanium alloys has arrived, with changes in design to improve flexibility, cyclic fatigue resistance and cutting efficiency, with more predictable results and less iatrogenic damage, but these modifications do not improve all the properties of endodontic files (, ).

The introduction of single use reciprocating systems has raised new perspectives for the preparation of root canals (, ). The learning curve of these systems and the cost savings compared to rotary systems with multiple instruments are arousing interest due to their simplification of the technique, since a single instrument is used to prepare the root canals (). This movement also disengages the instrument from dentin before it can lock into the canal and reduces the risk of root canal deformation and instrument separation (, ).

Nowadays, a number of different alloys have improved the properties of conventional NiTi. M-Wire, an alloy created by applying a heat treatment to conventional NiTi, is presented in Reciproc® (VDW, Munich, Germany) and Wave One® (Dentsply Maillefer, Ballaigues, Switzerland) (, ). Gold-Wire is another alloy that has recently appeared, enhancing the properties of ProTaper Universal® (Dentsply Maillefer, Ballaigues, Switzerland) and Wave One® (Dentsply Maillefer, Ballaigues, Switzerland), to create ProTaper Gold® (Dentsply Maillefer, Ballaigues, Switzerland) and Wave One Gold® (Dentsply Maillefer, Ballaigues, Switzerland) (, ), with a new thermal surface treatment (). CM-Wire is an alloy that gives Hyflex CM® (Coltene, Altstätten, Switzerland), Hyflex EDM® (Coltene, Altstätten, Switzerland) and Neoniti® (Neolix, Chatres-La-Foret, France) instruments controlled memory, which is very useful when treating root canals with severe curvatures (-), manufactured with wire cut electrical discharge machining (EDM) process (). The current systems have many different taper, movement, design, alloy, speed and torque characteristics and different numbers of files.

Currently, in terms of clinical implications of dentinal defects in long-term situations, no definitive conclusions can be made. Moreover, it is not known whether the improvements of nickel titanium alloys avoid the formation of defects. The purpose of this investigation was to examine the cutting area, root canal anatomy preservation and non-instrumented areas using F360® (Komet Dental, Lemgo, Germany), F6 SkyTaper® (Komet Dental, Lemgo, Germany), Hyflex EDM®, iRace® (FKG Dentaire, La Chaux-de-Fonds, Switzerland), Neoniti®, One Shape® (Micro-Mega, Besançon, France) ProTaper Next® (Dentsply Maillefer, Ballaigues, Switzerland), Reciproc®, Revo-S® (Micro-Mega, Besançon, France) and Wave One Gold® size 25 files.

Materials and methods

Methods similar to those mentioned in another scientific paper, which was published in 2015 by the same authors, were used ().

300 extracted permanent teeth with similar characteristics were divided randomly into 10 groups (n = 30). The selection criteria were: teeth with a single straight root and a circular or elliptical root canal. The endodontic opening was performed with a round diamond bur (Komet Dental, Lemgo, Germany) using water cooling, followed by an Endo-Z bur (Komet Dental, Lemgo, Germany). X-rays were used to estimate the working length hand files.

Permanent markers were used to draw a red marking on lingual/palatine and a black marking on vestibular part. Root lengths and section points were estimated in agreement with the length, using a 532 Vernier caliper (Mitutoyo, Takatsu-ku, Japan).

A hand piece (KMD Europa, Bilbao, Spain) equipped with ultrafine cutting disc (0.17mm) (Horico, Berlin, Germany) was used to section transversely the roots in thirds in the same manner as in Grande et al. (). A stereo microscope (Nikon, Tokyo, Japan) with Nikon camera (Nikon, Tokyo, Japan) was used to take pictures of all thirds (x15 magnification).

In thirds and overall, all groups were balanced by performing preinstrumentation analysis. A caliper was used to calculate mesiodistal width of coronal third of tooth No. 3, transferring to AutoCAD 2015 (Autodesk, San Rafael, USA) this calculation (5mm) to scale up and measure preinstrumentation areas. Scaling up was performed by loading the image of tooth No. 3 into AutoCAD 2015, after painting a 5mm mesial to distal line and squaring the mesial and distal edges of the coronal third, subsequently validating the sizes of other images against the abovementioned image. The SPSS 18 program (P<0.05) was used to make a preoperative analysis, using Levene´s and Welch´s tests, to evaluate variances and preinstrumentation areas. To balance the groups, some teeth would have been included and others discarded if significant differences had been achieved.

The #10 K-file (Dentsply Maillefer, Ballaigues, Switzerland) and epoxy glue were used to rebuild all of the teeth. The sections were adapted thanks to black and red markings that had previously been drawn. The 5.25% NaClO solution was used to flush root canals during instrumentation. The #10 K-file was used for patency filing, and #10 and #15 K-files were used to make a glide path. The root canals were instrumented using a circumferential movement. The protocols were as follows:

-Group 1 (F360®): F360 25/0.04 to 300rpm and 1.8 N·cm.

-Group 2 (F6 SkyTaper®): F6 SkyTaper 25/0.06 to 300rpm and 2.2 N·cm.

Group 3 (Hyflex EDM®): Hyflex EDM 25/0.05 to 500rpm and 2.5 N·cm.

-Group 4 (iRace®): R1 (15/0.06) and R2 (25/0.04) to 600rpm and 1.5 N·cm.

-Group 5 (Neoniti®): A1 (25/0.08) to 400rpm and 1.5 N·cm.

-Group 6 (One Shape®): One Shape 25/0.06 to 400rpm and 4 N·cm.

-Group 7 (ProTaper Next®): X1 (17/0.04) and X2 (25/0.06) to 300rpm and 2 N·cm.

-Group 8 (Reciproc®): R25 (25/0.08) to 300rpm and 2 N·cm.

-Group 9 (Revo-S®): SC1 (25/0.06), SC2 (25/0.04) and SU (25/0.06) to 350rpm and 0.8 N·cm.

-Group 10 (Wave One Gold®): Primary (25/0.07) to 350rpm and 2 N·cm.

In all groups, 2 mL of 5.25% NaClO2 mL of 0.9% saline solution, 2mL of 17% ethylenediamenetetracetic acid (EDTA) solution (Dentaflux, Algete, Spain) and 2 mL of 5.25% NaClO were flushed to finish the root canal treatments.

In the end, a microscope was used to keep the re-sectioned thirds, making pictures (x15 magnification). Postoperative areas of all thirds were calculated using a preoperative scale. The difference between preinstrumentation and postinstrumentation was estimated to determine the cutting areas (Figure 1). Non-instrumented areas and root canal anatomy preservation were studied by superimposing the preoperative and postoperative areas in the AutoCAD 2015 system (Figure 1). These parameters were calculated as the percentage of teeth in each third.

Figure 1

AutoCAD analysis of coronal (A to C), middle (D to F) and apical (G to I) thirds.

The SPSS 18 Statistics software package with normal distribution was used for statistical analysis and Levene´s and Welch´s tests to evaluate variances and cutting surfaces. Pearson´s chi-squared test was used to contrast the percentages of teeth of non-instrumented and root canal anatomy preservation.

Results

No file was fractured during the study. There were no significant differences in preinstrumentation areas (Table 1 and Table 2). The cutting areas were calculated by subtracting the postoperative area from the corresponding preoperative area (Table 1).

Table 1

Means of preinstrumentation and cutting area (mm2), and statistical analysis of preinstrumentation area.

		Preinstrumentation			Cutting area
Third	Sistema	Mean±SD	Min-Max	Test	Mean±SD	Min-Max
Coronal	F360F6HyflexiRaceNeonitiO.ShapeP.NextReciprocRevo-SWOG	1,066±0,1060,961±0,1221,003±0,0980,997±0,1010,976±0,1520,995±0,1161,073±0,1031,059±0,1831,038±0,1421,000±0,121	0,960-1,1720,839-1,0830,905-1,1010,896-1,0980,824-1,1280,879-1,1110,970-1,1760,876-1,2420,896-1,1800,879-1,121	Levene0.002	0,576±0,1021,208±0,1711,083±0,1770,824±0,0991,153±0,1260,938±0,0951,586±0,3011,510±0,2751,137±0,1931,047±0,193	0,474-0,6781,037-1,3790,906-1,2600,725-0,9231,027-1,2790,843-1,0331,285-1,8871,235-1,7850,944-1,3300,854-1,240
				Welch0.089
Middle	F360F6HyflexiRaceNeonitiO.ShapeP.NextReciprocRevo-SWOG	0,520±0,1080,551±0,0900,532±0,1340,532±0,1070,517±0,0860,505±0,0930,503±0,1560,547±0,0990,542±0,1510,517±0,094	0,412-0,6280,461-0,6410,398-0,6660,425-0,6390,431-0,6030,412-0,5980,347-0,6590,448-0,6460,391-0,6930,423-0,611	Levene0.005	0,278±0,0580,522±0,0840,707±0,1090,325±0,0480,789±0,1120,521±0,0810,477±0,0530,538±0,0650,676±0,0850,610±0,126	0,220-0,3360,438-0,6060,598-0,8160,277-0,3730,677-0,9010,440-0,6020,424-0,5300,473-0,6030,591-0,7610,484-0,736
				Welch0.095
Apical	F360F6HyflexiRaceNeonitiO.ShapeP.NextReciprocRevo-SWOG	0,217±0,0450,222±0,0380,269±0,0820,188±0,0570,273±0,0320,294±0,0750,224±0,0240,234±0,0510,252±0,0430,289±0,061	0,172-0,2620,184-0,2600,187-0,3510,131-0,2450,241-0,3050,219-0,3690,200-0,2480,183-0,2850,209-0,2950,228-0,350	Levene0.003	0,176±0,0300,352±0,0530,538±0,0710,176±0,0280,475±0,0590,354±0,0350,240±0,0300,355±0,0430,456±0,0510,431±0,047	0,146-2060,299-0,4050,467-0,6090,148-0,2040,416-0,5340,319-0,3890,210-0,2700,312-0,3980,405-0,5070,384-0,478
				Welch0.099
Overall	F360F6HyflexiRaceNeonitiO.ShapeP.NextReciprocRevo-SWOG	0,601±0,0640,578±0,0810,601±0,0920,572±0,0720,588±0,0640,598±0,0820,600±0,1020,613±0,1220,610±0,0990,602±0,082	0,537-0,6650,497-0,6590,509-0,6930,500-0,6440,524-0,6520,516-0,6800,498-0,7020,491-0,7350,511-0,7090,520-0,684	Levene0.019	0,343±0,0520,694±0,1000,776±0,0850,441±0,0680,805±0,0810,604±0,0660,768±0,1570,801±0,1400,756±0,0910,696±0,095	0,291-0,3950,594-0,7940,691-0,8610,373-0,5090,724-0,8860,538-0,6700,611-0,9250,661-0,9410,665-0,8470,601-0,791
				Welch0.063

Table 2

Statistical analysis of cutting area.

Cutting area
	Third
Test	Coronal	Middle	Apical	Overall
Levene	0.000	0.019	0.006	0.000
					Welch	0.000	0.000	0.000	0.000
Games-Howell	P.Next-F360 0.000Reciproc-F360 0.000F6-F360 0.000Hyflex-F360 0.000Neoniti-F360 0.000O.Shape-F360 0.000Revo-S-F360 0.000WOG-F360 0.004iRace-F360 0.024P.Next-iRace 0.001Reciproc-iRace 0.001F6-iRace 0.009Neoniti-iRace 0.004P.Next-O.Shape 0.006Reciproc-O.Shape 0.010	P.Next-F360 0.000Reciproc-F360 0.000F6-F360 0.000Hyflex-F360 0.000Neoniti-F360 0.000O.Shape-F360 0.000Revo-S-F360 0.000WOG-F360 0.001P.Next-iRace 0.002Reciproc-iRace 0.000F6-iRace 0.005Hyflex-iRace 0.000Neoniti-iRace 0.000O.Shape-iRace 0.004Revo-S-iRace 0.000WOG-iRace 0.005Hyflex-P.Next 0.013Revo-S-P.Next 0.007Neoniti-P.Next 0.000Neoniti-Reciproc 0.009Neoniti-F6 0.010Neoniti-O.Shape 0.008	Reciproc-F360 0.000F6-F360 0.000Hyflex-F360 0.000Neoniti-F360 0.000O.Shape-F360 0.000Revo-S-F360 0.000WOG-F360 0.000Reciproc-iRace 0.000F6-iRace 0.000Hyflex-iRace 0.000Neoniti-iRace 0.000O.Shape-iRace 0.000Revo-S-iRace 0.000WOG-iRace 0.000Reciproc-P.Next 0.002F6-P.Next 0.019Hyflex-P.Next 0.000Neoniti-P.Next 0.000O.Shape-P.Next 0.000Revo-S-P.Next 0.000WOG-P.Next 0.000Reciproc-Hyflex 0.002F6-Hyflex 0.003Hyflex-O.Shape 0.001O.Shape-Neoniti 0.027O.Shape-Revo-S 0.045	P.Next-F360 0.000Reciproc-F360 0.000F6-F360 0.000Hyflex-F360 0.000Neoniti-F360 0.000O.Shape-F360 0.000Revo-S-F360 0.000WOG-F360 0.000P.Next-iRace 0.009Reciproc-iRace 0.000F6-iRace 0.002Hyflex-iRace 0.000Neoniti-iRace 0.000O.Shape-iRace 0.029Revo-S-iRace 0.000WOG-iRace 0.001Neoniti-O.Shape 0.008

The ProTaper Next® system (1.586 ± 0.301 mm2) and Reciproc® system (1.510 ± 0.275 mm2) produced the largest cutting areas in the coronal third, which were significantly greater than with F360®, iRace® or One Shape® (Table 2) with both systems.

The Neoniti file system (0.,789 ± 0.,112 mm2 - 0.,475 ± 0.,059 mm2)) and the Hyflex EDM® ® file system (0.707.,707 ± 0..,109 mm2 - 0,.538 ± 0,.071 mm2) eliminated higher amounts of dentin in the middle and apical thirds.

In the middle third (Table 2), both ProTaper Next® and Reciproc® systems were superior to F360®, iRace® and ProTaper Next®, but Neoniti® was better than Reciproc®, F6 SkyTaper® and One Shape®. In the apical third (Table 2), the cutting areas of Neoniti® and Hyflex EDM® were greater than with F360®, iRace®, ProTaper Next® or One Shape®. Those of Hyflex EDM® were also better than with Reciproc® and F6 SkyTaper®. Overall, Neoniti® system (0.805 ± 0.081 mm2) and Reciproc® system (0.801 ± 0.140 mm2) obtained better results than other systems, both being superior to F360® and iRace®, while Neoniti was also better than One Shape® (Table 2).

Regarding the preservation of root canal anatomy (Table 3), Neoniti® and Hyflex EDM® obtained higher percentages in the coronal third (100%), Reciproc® and Wave One Gold® in the middle third (100%), and F360®, Reciproc® and Neoniti® in the apical third. However, there were no significant differences in any of the thirds (P>0.05).

Table 3

Root canal anatomy preservation (%), non-instrumented areas (%) and statistical analysis.

Root canal anatomy preservation	System	Coronal	Middle	Apical
	F360	90	96,67	100
	F6 SkyTaper	86,67	90	90
	Hyflex EDM	100	96,67	96,67
	iRace	80	90	96,67
	Neoniti	100	93,33	100
	One Shape	93,33	90	93,33
	Protaper Next	93,33	93,33	96,67
	Reciproc	93,33	100	100
	Revo-S	93,33	96,67	93,33
	Wave One Gold	86,67	100	93,33
	Pearson’s chi-squared	0.149	0.515	0.522
Non-instrumented areas	System	Coronal	Middle	Apical
	F360	33,33	23,33	13,33
	F6 SkyTaper	20	16,67	6,67
	Hyflex EDM	10	10	0
	iRace	23,33	16,67	13,33
	Neoniti	13,33	3,33	0
	One Shape	23,33	23,33	6,67
	Protaper Next	10	6,67	0
	Reciproc	10	3,33	0
	Revo-S	30	20	23,33
	Wave One Gold	20	3,33	0
	Pearson’s chi-squared	0,196	0,033	0,000

In relation to non-instrumented areas (Table 3), ProTaper Next®, Reciproc® and Hyflex EDM® scored lower percentages in the coronal third (10%), although there were not significant differences. Reciproc®, Neoniti® and Wave One Gold® were significantly better (P<0.05) in the middle third (3.33%) being significant better (P<0.05); and ProTaper Next®, Reciproc®, Hyflex EDM®, Neoniti® and Wave One Gold® were significantly superior (P<0.05) in the apical third (0%).

Discussion

This study compared the effects of ten endodontic systems (F360®, F6 SkyTaper®, Hyflex EDM®, iRace®, Neoniti®, One Shape®, ProTaper Next®, Reciproc®, Revo-S® and Wave One Gold®)of the same size but with different movements, tapers, designs, file numbers, speeds and torques in the cutting area, root canal anatomy preservation and non-instrumented areas. Three areas of root canal (the coronal, middle and apical thirds) were assessed in a similar fashion to that of Testa et al. (). Several studies have investigated the shaping ability in resin blocks, but the problem of these blocks is their distortion (, ). For this reason, the extracted human teeth were used in this study, likewise in Pedullà et al. ().

Regarding the use of AutoCAD in endodontics, this software was has been used to compare the efficacy of manual instrumentation and rotary and reciprocating instruments for removing root canal filling material in retreatments (, ,) the sealing quality of different systems (, ) and the working length loss () and apical transportation of multiple instrumentation systems (, ).

With regard to similar investigations into the shaping ability, Cabanillas et al. () compared manual instrumentation, ProTaper Universal®, ProTaper Next® and Wave One®. They concluded that there were no significant differences in the middle and apical thirds, and that Wave One® was significantly worse in the coronal third (P<0.05), probably due to the design of the file. Iqbal et al. () studied the percentage of instrumented areas with ProFile® and a hybrid technique using lqFiles and H-files at 1 and 3mm from working length; the hybrid technique with lqFiles was significantly better than the other techniques (P<0.05), but there were no significant differences between the two hybrid techniques at 3mm (P>0.05). In 2015 (), the authors of the present study used similar methodology to compare () F360®, RaCe®, Mtwo® and Hyflex CM® files, obtaining and no significant differences (P>0.05). However, all of the files used in the 2015 study had the same taper (4%) and size (#35), which are important factors in any investigations into the ability. Unlike in Cabanillas et al. (), significant differences in the middle and apical thirds were observed in the present study.

Concerning the cutting area results (Table 1), Reciproc® and ProTaper Next® obtained the highest means in the coronal third: 1.510 ± 0.275 mm2 and 1.586 ± 0.301 mm2 respectively. On the other hand, Neoniti® and Hyflex EDM® achieved the highest means in the middle and apical thirds: 0.789 ± 0.112 mm2 – 0.707 ± 0.109 mm2 and 0.475 ± 0.059 mm2 – 0.538 ± 0.071 mm2, respectively. Finally, Reciproc® (0.801±0.140mm2) and Neoniti® (0.805 ± 0.081 mm2) were significantly better overall. Ahmetoglu et al. () compared Reciproc®, Revo-S® and Self-Adjusting File® (SAF) by micro-computed tomography (μ-CT) in maxillary first molars, and found no significant differences between instrumentation systems (P>0.05). In another study, Saleh et al. () investigated Reciproc®, Wave One®, One Shape® and F360® 25 files using resin blocks and superimposing preoperative and postoperative images. The authors observed that Reciproc® and Wave One® were significantly better than One Shape® and F360® (P<0.05), probably because of the taper (8%) and the reciprocating movement. Moreover, Zeng et al. (4038) studied the cutting area of apical third of Reciproc®, One Shape®, Mtwo® and Revo-S® size 25 files in the apical third of mature molars with μ-CT and observed better results for Reciproc® (P<0.05), concluding that the reciprocating single-file system gave better results than continuous rotary systems. Extracted human teeth were used in this study as in those of Ahmetoglu et al. and Zeng et al. although unlike in Saleh et al., which superimposed preoperative and postoperative images, as in the present study ().

Root canal anatomy preservation is very important for three-dimensional obturation. The results (Table 3), showed that Neoniti® and Hyflex EDM® were the best systems in the coronal third (100%), Reciproc® and Wave One Gold® were the most stable (100%), and in apical thirds F360®, Reciproc® and Neoniti® obtained the best percentages in the apical thirds (100%). Non-instrumented areas can also jeopardize the endodontic treatment. For this reason, circumferential instrumentation is very important, and was used in all the groups. In this investigation the present study, ProTaper Next®, Reciproc® and Hyflex EDM® obtained the best percentage (10%) in the coronal third. In the middle third, Reciproc®, Neoniti® and Wave One Gold® were better (3.33%) than the other systems. Finally, ProTaper Next®, Reciproc®, Hyflex EDM®, Neoniti® and Wave One Gold® obtained the best percentage in the apical third (0%), (Table 3). Gergi et al. (, ) compared the root canal anatomy preservation and non-instrumented areas with Reciproc®, Wave One® and TF® size 25 files, finding no significant differences in non-instrumented areas (P>0.05), but better root canal anatomy preservation results with TF® (P<0.05). De-Deus et al. () investigated non-instrumented areas for size 25 and 40 Reciproc®, Wave One® and BioRace® files and concluded that there were no significant differences between all any of the systems (P>0.05). Unlike Gergi et al. and De-Deus et al., the present study found significant differences in non-instrumented areas in the middle and apical thirds, but Reciproc® was significantly better (P<0.05), probably due to its S cross-section, reciprocating movement and taper.

Conclusions

In cutting area, ProTaper Next® and Reciproc® were superior in the coronal third, Neoniti® and Hyflex EDM® in the middle and apical thirds, and Neoniti® and Reciproc® overall. Regarding root canal anatomy preservation, all the systems obtained similar results. In non-instrumented areas, the systems were similar in the coronal third, but Reciproc®, Neoniti® and Wave One Gold® were better in the middle third, and ProTaper Next®, Reciproc®, Hyflex EDM®, Neoniti®, and Wave One Gold® were better in the apical third.