doi:10.1111/iej.12296
Effects of three nickel titanium instrument systems on root canal geometry assessed by micro-computed tomography
R. Gergi1, N. Osta1, G. Bourbouze2, C. Zgheib1, R. Arbab-Chirani2 & A. Naaman1 1
Department of Endodontics, Saint-Joseph University, Beirut, Lebanon; and 2Department of Endodontics, Brest University, Brest, France
Abstract Gergi R, Osta N, Bourbouze G, Zgheib C, ArbabChirani R, Naaman A. Effects of three nickel titanium instrument systems on root canal geometry assessed by microcomputed tomography. International Endodontic Journal.
Aim To compare and evaluate the shaping ability of several nickel titanium instrument systems with different motions: two reciprocating single-file systems (Reciproc and WaveOne) and one continuous rotation/reciprocation full-sequence system [Twisted File (TF) Adaptive] using micro-computed tomography. Methodology A total of forty-eight mesial canals of mandibular molars with two separate root canals and severe angles of curvature were selected. Canals were divided randomly to one of three experimental groups: group 1, reciprocating instrumentation with Reciproc R25, group 2, reciprocating with the Primary WaveOne file and group 3 ‘Adaptive Rotary Motion’ with Twisted Files. Each group consisted of 16 root canals. Canals were scanned before and after root canal preparation, with a resolution of 20 lm using a micro-computed tomography system. The following parameters were assessed: changes in dentine volume, percentage of unshaped canal walls, degree of canal transportation and centring ability. Data were analysed using analysis of variance and Tukey’s post hoc tests test to explore a significant difference in mean dentine removal, mean percentage of noninstrumented
canals, mean degree of canal transportation and centring ratio between groups in the apical third and along the entire root canal. The level of significance was set at a = 0.05. Results Preoperatively, there were no differences regarding root canal curvature and volume between experimental groups (P > 0.05). Overall instrumentation led to enlarged canal shapes with no evidence of preparation errors. None of the three groups was able to shape completely the root canal system. Mean dentine removal along the entire canal and in the apical third was significantly higher with Reciproc when compared with TF Adaptive and WaveOne (P = 0.013). Mean degree of canal transportation was significantly lower with TF Adaptive (P < 0.0001) followed by WaveOne and highest with Reciproc in the apical third and along the entire root canal. Conclusions None of the NiTi systems was able to instrument completely the entire root canal. Reciprocation and Adaptive Motions were found to cut dentine efficiently to full working length, with no procedural errors. The TF Adaptive system maintained the original canal anatomy with less canal transportation and better centring ability. Keywords: canal transportation, micro-CT, reciprocating, shaping. Received 8 February 2014; accepted 5 April 2014
Introduction Correspondence: Richard Gergi, Department of Endodontics, Saint-Joseph University, Damascus Street, Beirut, Lebanon (e-mail: [email protected]).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Recently, several new reciprocating NiTi systems such as Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) have been
International Endodontic Journal
1
Canal preparation assessed by micro-CT Gergi et al.
introduced. Single-use, reciprocating motion and M-wire alloy are the main characteristics of these instruments. The M-wire alloy increases flexibility and improves its resistance to cyclic fatigue (Stern et al. 2012, Marzouk & Ghoneim 2013). Furthermore, the reciprocating motion is similar to balanced force technique that has been shown to maintain root canal curvature (Abou-Rass et al. 1980, Versiani et al. 2013). Twisted File Adaptive (TF Adaptive), a combined continuous rotation and reciprocating motion has been developed by SybronEndo (Orange, CA, USA) with three unique design features, namely R-phase heat treatment, twisting of the metal and special surface conditioning (Gambarini et al. 2012a,b). The manufacturer claims that this adaptive technology and twisted file design using R-phase treatment increases flexibility and allows the file to adjust to intra-canal torsional forces depending on the amount of pressure placed on the file (Gambarini et al. 2013). The aim of this study was to evaluate and compare the effect of different NiTi instrumentation techniques on canal volume, percentage of unshaped canal walls, canal transportation and centring ability when using Reciproc, WaveOne and TF Adaptive. High-definition micro-computed tomography (lCT) was used on extracted human mandibular molars with two separate mesial canals with acute curvature to evaluate the cutting ability of these systems. The null hypothesis was that no difference could be detected in the analysed parameters between the three preparation techniques.
Materials and methods Experimental teeth A total of twenty-four extracted human mandibular molars were selected from a pool of extracted teeth. Inclusion criteria stipulated that the tooth had a curved mesial root 25° < a < 35° (Schneider 1971), with two separate mesial canals, two separate apical foramina and a canal width at the apex of approximately size 15. Access cavities were prepared using a no. 4 high-speed round carbide bur (Dentsply Maillefer) with water spray. A size 15 K-file (Dentsply Maillefer) was placed into the canal until it was visible at the apical foramen and the working length (WL) established 0.5 mm short of this length. Teeth with apical diameters larger than size 15 were excluded from the study. A total of six small grooves were made on the external surface of the root using a HiDi 520 (Dentsply
2
International Endodontic Journal
Maillefer) round diamond bur and filled with composite (Z250; 3M ESPE, St Paul, MN, USA). These composite-filled grooves acted as reference points at levels 2.0, 4.0, 6.0, 8.0, 10.0 and 12.0 mm from the apex of the tooth for the superimposition of the lCT images obtained before and after instrumentation. Root canals (n = 48) were randomly assigned to one of the three experimental groups. Randomization was stratified to ensure that mesio-buccal and mesiolingual canals were distributed equally to each group consisting of 16 root canals. Group 1: Reciproc group (n = 16) The Reciproc R25 instrument size 25 and 0.08 taper over the first 3 mm was used in a reciprocating, slow in-and-out pecking motion according to the manufacturer’s instruction. The instrument R25 was operated in a reciprocating motion powered by a torque-limited electric motor (VDW Silver, Munich, Germany) using the preset adjustments. The instrument was introduced into the canal until resistance was felt and then moved in an apical direction using in-and-out pecking motion about 3 mm in amplitude with light apical pressure. After three pecking motions, the instrument was removed and cleaned, and the canal was irrigated with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. This protocol was repeated until WL was reached by the R25 instrument. Group 2: WaveOne group (n = 16) A primary reciprocating WaveOne file size 25 and 0.08 taper was used in a reciprocating, slow in-andout pecking motion according to the manufacturer’s instructions. The WaveOne instrument was operated in a reciprocating motion powered by a torque-limited electric motor (VDW Silver) using the manufacturer configuration setup. The instrument was introduced into the canal until resistance was felt and moved in an apical direction using in-and-out pecking motion about 3 mm in amplitude with light apical pressure. After three pecking motions, the instrument was removed and cleaned, and the canal was irrigated with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. This protocol was repeated until WL was reached by the R25 instrument. Group 3: TF Adaptive group (n = 16) Twisted File Adaptive instruments were operated with the Elements Adaptive Motion Technology:
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
1. The shaping procedure commenced with TFA size 25 and 0.08 taper. The coronal 1/3 or 2/3 of the root canal was shaped if passive penetration was possible. 2. TFA size 25 and 0.06 taper was inserted and used up to 2 mm short of WL. 3. Shaping continued with 0.04 taper size 25 instrument to the WL. 4. TFA size 25, 0.06 taper was taken to WL. 5. A 0.08 taper size 25 instrument was taken to WL. Canals were irrigated between instruments with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. All groups After instrumentation, all root canals were irrigated with 3 mL of 5.25% NaOCl. A disposable syringe was used on which an Endo-Eze (Ultradent, South Jordan, UT, USA) irrigator tip was mounted. Glyde (Dentsply Maillefer) was used as a lubricant during instrumentation and when root canal instrumentation was completed 1 mL of 15% EDTA (Wizard; Rehber Kimya San., Istanbul, Turkey) was applied for 1 min and the canals flushed again with 3 mL of NaOCl. Each instrument was changed after three canals. Consequently, the final apical preparation resulting was standardized to size 25, 0.08 taper for all groups.
lCT scanning procedures and evaluation Before preparation and scanning, each experimental tooth was mounted on scanning electron microscopy carriers (014001-T; Bal-Tec AG, Balzers, Liechtenstein) to allow exact repositioning in the scanning system. Although the mounting device ensured
almost exact repositioning of the specimens, superimposition was further calculated with newly developed software (IPL Register 1.01; Scanco Medical, Br€ uttisellen, Switzerland), as previously reported by Paque et al. (2009). The composite-filled grooves were also used as reference points to superimpose the pre- and postoperative images. The final exact superimposition of the teeth before and after preparation was with a precision better than one voxel. Specimens were scanned initially and after root canal preparation at 140 kV and 200 lA with an isotropic resolution of 20 lm by using a commercially available lCT system (VTomeX, Wunstorf, Germany). All the scans were reoriented with respect to the x-, y- and z-axes using the imaging software MicroView (GE Pre-clinical Imaging, General Electric, London, UK). The volume of root canals and the surface area were evaluated in the apical, middle and coronal third of the canals using specially developed software (IPL V5.06B; Scanco Medical). The region of interest was selected extending from the floor of the pulp chamber to the apex of the roots. The apical, middle and coronal third regions of the canals were determined by calculating the number of cross-sectional slices from the apex of the tooth to the floor of the pulp chamber and then dividing by three. The resulting colour-coded root canal models (green indicates preoperative and red indicates postoperative canal surfaces) enabled quantitative comparison of the matched root canals before and after shaping (Paque et al. 2011, Fig. 1).
Measurement of canal volume and surface area Increases in canal volume and surface areas (i.e. amount of dentine removal) were calculated by
Figure 1 Representative example of pre- (green) and postoperative (red) micro-CT images. Green area is unprepared; red area is prepared.
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
International Endodontic Journal
3
Canal preparation assessed by micro-CT Gergi et al.
subtracting the scores for the treated canals from those recorded for the untreated counterparts. Matched images of the surface areas of the canals before and after preparation were examined to evaluate the amount of noninstrumented canal wall surface. This parameter was expressed as a percentage of the number of static voxel surface to the total number of surface voxels. The software counts a surface voxel as belonging to any given structure when the full voxel belongs to it. Therefore, to be counted as instrumented, at least one full voxel (i.e. 20 lm) had to be registered as removed from the preoperative canal model after superimposition (Stern et al. 2012). The pre- and post-instrumentation scans were superimposed to determine canal transportation and centring ability in the mesio-distal direction.
Evaluation of canal transportation To compare the degree of canal transportation, the technique developed by Gambill et al. (1996) was used. Using the 3D viewer and analysis software, MicroView, two-dimensional cross-sectional images of the teeth were produced. Transportation was evaluated by two operators at six different equidistant levels, predetermined with the line measuring tool of the MicroView software (GE Pre-clinical Imaging): two equidistant levels in the apical third, two equidistant levels in the mid-third and two equidistant levels in the coronal third. The examiners were trained and calibrated prior to measuring the experimental volume. The dimensions were determined by measuring the shortest distance from the edge of the uninstrumented canal to the edge of the tooth in both mesial and distal directions and then compared with the values measured from the prepared canals. The measurements of the distance of the points of interest were
taken with the line measuring tool of the MicroView software and averaged for each level. The following formula was used for the calculation of transportation: jða1 a2 Þ ðb1 b2 Þj where a1 is the shortest distance from the mesial edge of the curved root to the mesial edge of the uninstrumented canal; b1 is the shortest distance from distal (furcation) edge of the curved root to the distal edge of the uninstrumented canal; a2 is the shortest distance from the mesial edge of the curved root to the mesial edge of the instrumented canal; b2 is the shortest distance from distal (furcation) edge of the curved root to the distal edge of the instrumented canal (Fig. 2). According to this formula, a result of ‘0’ indicates no canal transportation. A result other than ‘0’ means that transportation had occurred.
Evaluation of centring ability According to Gambill et al. (1996), ‘the mean centring ratio’ indicates the ability of the instrument to stay centred in the canal. This ratio was calculated for each section using the following ratio: ða1 a2 Þ ðb1 b2 Þ or ðb1 b2 Þ ða1 a2 Þ If these numbers are not equal, the lower figure is considered as the numerator of the ratio. According to this formula, a result of ‘1’ indicates perfect centring.
Data presentation and statistical analysis The normality of the variable distribution in each group was verified using Kolmogorov–Smirnov tests.
Figure 2 Superimposed micro-CT images of the pre- and postoperative images. a1 = shortest distance from the mesial aspect of the root to the periphery of the uninstrumented canal. a2 = shortest distance from the mesial aspect of the root to the periphery of the prepared canal. b1 = shortest distance from the distal aspect of the root to the periphery of the uninstrumented canal. b2 = shortest distance from the distal aspect of the root to the periphery of the prepared canal.
4
International Endodontic Journal
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
One-way analysis of variance was used to test the comparability amongst groups concerning preoperative root canal volumes, preoperative canal angles and radius. One-way analysis of variance followed by post hoc tests Tukey’s Honestly Significant Different test (HSD) was conducted to explore a significant difference in mean dentine removal and in mean percentage of noninstrumented canals between the three shaping procedures: Reciproc, WaveOne and TF Adaptive in the apical third and in the entire root canal. The level of significance was set at a = 0.05. One-Sample t-test was conducted to determine whether the mean dentine removal and if the mean percentage of noninstrumented root canals were significantly different from 0. One-way analysis of variance followed by Tukey HSD test multiple comparisons was conducted to look at a significant difference in mean degree of canal transportation and in centring ratio between the three shaping procedure in each section of the root canal, and along the entire root canal. Onesample t-tests were conducted to find out if the mean degree of canal transportation was significantly different from 0. The level of significance was set at a = 0.05. One-sample t-tests were conducted to determine whether the mean centring ratio in each canal section and in each shape procedure was significantly different from 1 or 0. The level of significance was set at a = 0.05.
Results Preoperatively, there were no significant differences regarding root canal curvature and volume amongst experimental groups (P > 0.05).
Dentine removal along the entire canal The mean dentine removal along the entire canal was significantly different amongst groups (P = 0.013 and was significantly higher with the Reciproc system. No significant difference was found between WaveOne and TF Adaptive (P = 0.644; Table 1).
Dentine removal in the apical third The mean dentine removal in the apical third was significantly different amongst groups (P < 0.0001 and was significantly higher with the Reciproc
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Table 1 Amount of dentine removal (mean SD) in the apical third and in the entire root canal Dentine removal (mm3) In the entire canal Twisted File Adaptive Reciproc WaveOne In the apical third TF Adaptive Reciproc WaveOne
n
Mean
SD
Minimum
Maximum
16
1.07a
0.60
0.13
2.87
16 16
1.61b 0.84a
0.95 0.62
0.23 0.05
3.28 2.14
16 16 16
0.07a 0.19b 0.08a
0.04 0.10 0.06
0.01 0.03 0.01
0.15 0.35 0.21
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
system. No significant difference was found between WaveOne and TF Adaptive (P = 0.932; Table 1).
Noninstrumented surface along the entire canal The mean percentage of noninstrumented surface along the entire canal was significantly different amongst groups (P = 0.021 and was significantly lower with Reciproc. No significant difference was found between WaveOne and TF Adaptive (P = 0.483; Table 2, Fig. 3).
Noninstrumented surface in the apical third The mean percentage of noninstrumented surface in the apical third was significantly different amongst groups (P = 0.044) and was significantly lower with Reciproc. No significant difference was found between WaveOne and TF Adaptive (P = 0.692; Table 2).
Table 2 Percentage of noninstrumented surface area (mean SD) in the apical third and in the entire root canal Percentage
n
In the entire canal Twisted File 16 Adaptive Reciproc 16 WaveOne 16 In the third apical TF Adaptive 16 Reciproc 16 WaveOne 16
Mean
SD
Minimum
Maximum
28.77a
18.65
5.10
66.50
20.55b 35.31a
10.27 19.13
1.30 10.25
32.30 67.60
35.48a 25.00b 40.30a
17.03 18.59 16.55
7.70 0.90 16.40
67.30 56.90 76.40
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
International Endodontic Journal
5
Canal preparation assessed by micro-CT Gergi et al.
Canal transportation
Figure 3 Representative three-dimensional example of mesial canals in mandibular molar, showing noninstrumented surface areas (dark blue).
Surface area increase
Centring ratio
Mean increase in surface area within the apical third along the entire root canal was significantly higher with Reciproc (P < 0.001; ANOVA). No significant difference was found with WaveOne and TF Adaptive (P = 0.910; Table 3).
In each section of the root canal, there was a significant difference in mean centring ratio between the three shaping techniques (P < 0.0001). In the cervical section of the root canal, the mean centring ratio was significantly higher with TF Adaptive
Table 3 Surface area changes (mean SD) in the apical
third and in the entire root canal Surface area (mm2)
n
In the entire canal Twisted File 16 Adaptive Reciproc 16 WaveOne 16 In the apical third TF Adaptive 16 Reciproc 16 WaveOne 16
Mean
SD
Minimum
Maximum
Table 4 Absolute values of mean canal transportation (mm SD) for the coronal, middle, and apical thirds after preparation with TF Adaptive, Reciproc and WaveOne Mean canal transportation Twisted File Adaptive
a
13.45
5.10
36.30
46.12b 38.22a
16.23 14.23
1.30 10.25
22.10 32.60
Reciproc
25.26a 39.00b 28.10a
13.00 17.43 18.51
4.70 5.10 3.20
40.30 26.40 34.50
WaveOne
37.56
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
6
In each section of the root canal, there was a significant difference in mean degree of canal transportation between the three shaping techniques (P < 0.0001). In the cervical third, the transportation was significantly less with TF Adaptive (P < 0.0001). No significance difference was found between Reciproc and Wave One (P = 0.59). In the middle third, transportation was significantly less with TF Adaptive (P < 0.0001) followed by WaveOne and Reciproc (Table 4). In the apical third, the mean degree of canal transportation was significantly less with TF Adaptive (P < 0.0001), followed by WaveOne (P < 0.0001) and highest with the Reciproc system (P < 0.0001) (Table 4). The mean degree of canal transportation was significantly lower with TF Adaptive (P < 0.0001) followed by WaveOne and highest with Reciproc. In each section of the root canal, and with each shaping procedure, the mean degree of canal transportation was significantly different from 0 (P < 0.0001). TF Adaptive instruments had the least amount of root canal transportation with a significant difference when compared with Reciproc and WaveOne.
International Endodontic Journal
N
Level
16 16 16 16 16 16 16 16 16
Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical
Mean SD 0.02 0.02 0.02 0.05 0.06 0.07 0.05 0.04 0.04
0.07a 0.06a 0.04a 0.09b 0.08c 0.07c 0.10b 0.09d 0.08d
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
(P < 0.0001). There was no significant difference between Reciproc and WaveOne (P = 0.329). In the middle and apical sections of the root canal, the mean centring ratio was significantly higher with the TF Adaptive system (P < 0.0001) followed by WaveOne and was minimal with Reciproc (P < 0.05; Table 5).
Discussion In the current study, the shaping ability of two reciprocating single-file systems (Reciproc and WaveOne) and one combined continuous/reciprocation motion (TF Adaptive) was evaluated by lCT. The experimental design had several variables: the manufacturing process, the number of files used and movement kinematic. It is not possible to isolate the influence of each variable on the results. The Reciproc and the WaveOne files alternate between clockwise (CW) and counter-clockwise rotation during the shaping procedure. According to the manufacturer, the fact that the rotation in the cutting direction is larger than the reverse rotation helps the reciprocating files to progress along the canal path, whilst respecting root canal anatomy. The reciprocating movement relieves stress on the instrument and reduces the risk of cyclic fatigue caused by tension and compression (B€ urklein et al. 2011). The newly introduced TFA system uses an existing file set called Twisted Files in conjunction with the new Elements Motor featuring Adaptive Motion. According to the manufacturer, the Adaptive Motion relies on a patented algorithm that changes the motion of the file based on the applied load. This
Table 5 Mean and standard deviation (SD) of the centring ratio (mm SD) for the coronal, middle and apical thirds after preparation with TF Adaptive, Reciproc and WaveOne Mean centring ratio Twisted File Adaptive Reciproc
WaveOne
n
Level
16 16 16 16 16 16 16 16 16
Cervical Median Apical Cervical Median Apical Cervical Median Apical
Mean SD 0.93 0.93 0.94 0.54 0.58 0.52 0.618 0.643 0.610
0.05a 0.06a 0.05a 0.12b 0.18c 0.089c 0.074b 0.072d 0.062d
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
patented algorithm ‘adapts’ to canal conditions based on the amount of pressure on the file. When the file is not loaded or lightly loaded, it will rotate continuously in a CW direction with no backward movement. When the file is loaded, reciprocation angles vary: 370° forward and 20° to 50° backwards, based on file load. In the present study, mesial roots with acute curves of mandibular molars were selected because these contain canals that are often narrow and curved in two planes increasing the level of instrumentation difficulty (Berutti & Fedon 1992). The focus of the study was clearly on the quality of the final canal shape. However, the limitations of the current study are clear; extracted human teeth were instrumented in a set-up that differs from the clinical situation. Patient comfort and other strictly clinical outcomes could thus not be investigated. Furthermore, only one experienced operator performed the operative procedures, rendering the experiment better standardized. However, conclusions cannot directly be extrapolated to the average potential user of the techniques under investigation. The effect of canal instrumentation was analysed quantitatively by using a set of parameters including canal volume and un-instrumented canal surface area. All these results are mean values over the entire canal length and over the apical third, measured three-dimensionally using lCT. Accuracy and reproducibility of the lCT system have been verified previously, and it is accepted as an important scientific tool for the effect analysis of different shaping techniques (Gambarini et al. 2012a,b). Electron microscopy carriers and the use of newly developed software (IPL Register 1.01; Scanco Medical), as previously reported by Paque et al. (2011) allowed exact repositioning and superimposition in the scanning system with a precision better than one voxel. Root canal instrumentation resulted in significant gains in canal volumes and surface areas. Overall, the highest mean increase of the parameters was observed with the Reciproc group when compared with WaveOne and TF Adaptive. The cutting ability of root canal instruments is a complex interrelationship of different parameters such as the cross-sectional design, helical and rake angle, metallurgical properties, surface treatments of the instrument and movement kinematics (Capar et al. 2013). Canal volume is a variable used to analyse the effects of canal instrumentation on dentine removal (Peters et al. 2010, Berutti et al. 2012a,b).
International Endodontic Journal
7
Canal preparation assessed by micro-CT Gergi et al.
Over-instrumentation of the root canal could result in excessive thinning of the root. In the present study, root canal instrumentation resulted in an increase in canal volume and surface area with Reciproc showing a greater amount of removed dentine than WaveOne and TF Adaptive. None of the three NiTi systems was able to instrument completely the entire root canal wall; approximately 20–35% of the canal surface area was found uninstrumented in the three groups after preparation, which is consistent with previous studies (Paque et al. 2011, Versiani et al. 2013). These untouched areas may harbour unaffected residual bacteria biofilms and serve as a potential cause of persistent infection and poor treatment outcome (Alves et al. 2011, Dietrich et al. 2012). To date, there are no studies comparing root canal transportation of TF Adaptive to reciprocating NiTi instruments Reciproc and WaveOne. With similar apical preparation diameter, the results revealed that TF Adaptive files produced significantly less transportation and a better centring ratio followed by WaveOne and by Reciproc system. The Adaptive Motion combined with the flexibility of the TF files may explain the shaping results obtained with the TF Adaptive system (Zhao et al. 2013). Additionally, the use of the multiple file TF Adaptive system with smaller tapered instruments reaching WL before instrument size 25 taper 0.08 can also be an important factor in reducing the amount of transportation (Gergi et al. 2010, Marzouk & Ghoneim 2013). Berutti et al. (2011) revealed a significant decrease in canal length mainly because of straightening of root canal curves after instrumentation with the WaveOne single-file primary reciprocating file (size 25 taper 8%). Since WaveOne and Reciproc instruments are used without first performing preliminary coronal enlargement, this may result in a greater engagement of the flutes and may produce consequently more torque and/or applied pressure on the file resulting in a higher incidence of canal transportation (Pak & White 2011). Canal transportation was higher with Reciproc compared with WaveOne, especially in the apical third. Despite the Reciproc and WaveOne instruments having similarities (same alloy, reciprocation movement and tip size), their different cross-sectional designs may explain the greater cutting ability and canal transportation of Reciproc (Versiani et al. 2013). Reciproc size 25 taper 0.08 has a sharp double-cutting edge S-shaped geometry, whereas WaveOne is characterized by a modified triangular cross section with radial lands at the tip and a convex triangular cross section in the
8
International Endodontic Journal
middle and coronal portion of the instrument. The WaveOne modified cross section results in lower cutting efficiency and less chip space (You et al. 2011). Coronal enlargement, canal scouting and preliminary creation of a glide path are fundamental for the safer use of NiTi rotary instrumentation. A recent study has shown that the WaveOne Primary instrument produced less modification in the canal curvature if used with a glide path, suggesting that the presence of a larger canal improves the performance of the instrument (Berutti et al. 2012a,b).
Conclusion Within the limits of this study, the null hypothesis that there is no difference between Reciproc, WaveOne and TF Adaptive in the preparation of mesiobuccal and mesio-lingual root canals of mandibular molars was rejected. The TF Adaptive system maintained the original canal anatomy with less modification of the canal curvature compared with the WaveOne and Reciproc system. Overall instrumentation led to enlarged canal shapes with no evidence of preparation errors; however, none of the three NiTi systems was able to shape completely the root canal.
References Abou-Rass M, Frank AL, Glick DH (1980) The anticurvature filing method to prepare the curved root canal. Journal of the American Dental Association 101, 792–4. Alves FR, Almeida BM, Neves MA, Moreno JO, R^ ocßas IN, Siqueira JF Jr (2011) Disinfecting oval shaped root canals: effectiveness of different supplementary approaches. Journal of Endodontics 37, 496–501. Berutti E, Fedon G (1992) Thickness of cementum dentin/ dentin in mesial roots of mandibular first molars. Journal of Endodontics 18, 545–8. Berutti E, Chiandussi G, Paolino DS et al. (2011) Effect of canal length and curvature on working length alteration with WaveOne reciprocating files. Journal of Endodontics 37, 1687–90. Berutti E, Chiandussi G, Paolino DS et al. (2012a) Canal shaping with WaveOne Primary reciprocating files and ProTaper system: a comparative study. Journal of Endodontics 38, 505–9. Berutti E, Paolino DS, Chiandussi G et al. (2012b) Root canal anatomy preservation of WaveOne reciprocating files with or without glide path. Journal of Endodontics 38, 101–4. B€ urklein S, Hinshitza K, Dammashke T, Sch€ afer E (2011) Shaping ability and cleaning effectiveness of two single-file systems in severely curved root canals of extracted teeth:
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
Reciproc and WaveOne versus Mtwo and ProTaper. International Endodontic Journal 45, 449–61. Capar ID, Ertas H, Ok E, Arslan H, Ertas ET (2013) Comparative study of different novel nickel-titanium rotary systems for root canal preparation in severely curved root canals. Journal of Endodontics 10, 1–5. Dietrich MA, Kirkpatrick TC, Yaccino JM (2012) In vitro canal and isthmus debris removal of the self-adjusting file, k3 and WaveOne files in the mesial root of human mandibular molars. Journal of Endodontics 38, 1140–4. Gambarini G, Gergi R, Naaman A, Osta N, Al Sudani D (2012a) Cyclic fatigue of twisted file rotary NiTi instruments used in reciprocating motion. International Endodontic Journal 45, 802–6. Gambarini G, Rubini AG, Al Sudani D et al. (2012b) Influence of different angles of reciprocation on the cyclic fatigue of nickel-titanium endodontic instruments. Journal of Endodontics 38, 1408–11. Gambarini G, Testarelli L, De luca M et al. (2013) The influence of three different instrumentation techniques on the incidence of postoperative pain after endodontic treatment. Annali di Stomatologia e dell’Istituto Superiore di Odontoiatria 20, 152–5. Gambill JM, Alder M, del Rio CE (1996) Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography. Journal of Endodontics 22, 369–75. Gergi R, Rjeily JA, Sader J, Naaman A (2010) Comparison of canal transportation and centering ability of twisted files, Pathfile-ProTaper system, and stainless steel hand K-files by using computed tomography. Journal of Endodontics 36, 904–7. Marzouk AM, Ghoneim AG (2013) Computed tomographic evaluation of canal shape instrumented by different kine-
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
matics rotary nickel-titanium systems. Journal of Endodontics 39, 906–9. Pak JG, White SN (2011) Pain prevalence and severity before, during and after root canal treatment: a systematic review. Journal of Endodontics 37, 427–38. Paque F, Laib A, Gautschi H, Zehnder M (2009) Hard-tissue debris accumulation analysis by high-resolution computed tomography scans. Journal of Endodontics 35, 1056–9. Paque F, Zehnder M, De-Deus G (2011) Microtomographybased comparison of reciprocating single-file F2 ProTaper technique versus rotary full sequence. Journal of Endodontics 37, 1394–7. Peters OA, Boessler C, Paque F (2010) Root canal preparation with a novel nickel titanioum instrument evaluated with micro-computed tomography; canal surface preppartion over time. Journal of Endodontics 36, 1068–72. Schneider SW (1971) A comparison of canal preparations in straight and curved root canals. Oral Surgery Oral Medicine Oral Pathology Oral Radiology Endodontology 32, 271–5. Stern S, Patel S, Foschi F et al. (2012) Changes in centering and shaping ability using three nickel-titanium instrumentation techniques analysed by micro-computed tomography (lCT). International Endodontic Journal 45, 514–23. Versiani MA, Leoni GB, Steier L et al. (2013) Micro-computed tomography study of oval-shaped canals prepared with the Self-adjusting File, Reciproc, WaveOne, and ProTaper Universal systems. Journal of Endodontics 39, 1060–6. You SY, Kim HC, Bae KH et al. (2011) Shaping ability of reciprocating motion in curved root canals: a comparative study with micro-computed tomography. Journal of Endodontics 37, 1296–300. Zhao D, Peng B, Haapsalo M (2013) Micro-computed tomograohy evaluation of the preparation of mesiobuccal root canals in maxillary first molars with Hyflex CM, Twisted Files and K3 instruments. Journal of Endodontics 39, 385–8.
International Endodontic Journal
9
Effects of three nickel titanium instrument systems on root canal geometry assessed by micro-computed tomography
R. Gergi1, N. Osta1, G. Bourbouze2, C. Zgheib1, R. Arbab-Chirani2 & A. Naaman1 1
Department of Endodontics, Saint-Joseph University, Beirut, Lebanon; and 2Department of Endodontics, Brest University, Brest, France
Abstract Gergi R, Osta N, Bourbouze G, Zgheib C, ArbabChirani R, Naaman A. Effects of three nickel titanium instrument systems on root canal geometry assessed by microcomputed tomography. International Endodontic Journal.
Aim To compare and evaluate the shaping ability of several nickel titanium instrument systems with different motions: two reciprocating single-file systems (Reciproc and WaveOne) and one continuous rotation/reciprocation full-sequence system [Twisted File (TF) Adaptive] using micro-computed tomography. Methodology A total of forty-eight mesial canals of mandibular molars with two separate root canals and severe angles of curvature were selected. Canals were divided randomly to one of three experimental groups: group 1, reciprocating instrumentation with Reciproc R25, group 2, reciprocating with the Primary WaveOne file and group 3 ‘Adaptive Rotary Motion’ with Twisted Files. Each group consisted of 16 root canals. Canals were scanned before and after root canal preparation, with a resolution of 20 lm using a micro-computed tomography system. The following parameters were assessed: changes in dentine volume, percentage of unshaped canal walls, degree of canal transportation and centring ability. Data were analysed using analysis of variance and Tukey’s post hoc tests test to explore a significant difference in mean dentine removal, mean percentage of noninstrumented
canals, mean degree of canal transportation and centring ratio between groups in the apical third and along the entire root canal. The level of significance was set at a = 0.05. Results Preoperatively, there were no differences regarding root canal curvature and volume between experimental groups (P > 0.05). Overall instrumentation led to enlarged canal shapes with no evidence of preparation errors. None of the three groups was able to shape completely the root canal system. Mean dentine removal along the entire canal and in the apical third was significantly higher with Reciproc when compared with TF Adaptive and WaveOne (P = 0.013). Mean degree of canal transportation was significantly lower with TF Adaptive (P < 0.0001) followed by WaveOne and highest with Reciproc in the apical third and along the entire root canal. Conclusions None of the NiTi systems was able to instrument completely the entire root canal. Reciprocation and Adaptive Motions were found to cut dentine efficiently to full working length, with no procedural errors. The TF Adaptive system maintained the original canal anatomy with less canal transportation and better centring ability. Keywords: canal transportation, micro-CT, reciprocating, shaping. Received 8 February 2014; accepted 5 April 2014
Introduction Correspondence: Richard Gergi, Department of Endodontics, Saint-Joseph University, Damascus Street, Beirut, Lebanon (e-mail: [email protected]).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Recently, several new reciprocating NiTi systems such as Reciproc (VDW, Munich, Germany) and WaveOne (Dentsply Maillefer, Ballaigues, Switzerland) have been
International Endodontic Journal
1
Canal preparation assessed by micro-CT Gergi et al.
introduced. Single-use, reciprocating motion and M-wire alloy are the main characteristics of these instruments. The M-wire alloy increases flexibility and improves its resistance to cyclic fatigue (Stern et al. 2012, Marzouk & Ghoneim 2013). Furthermore, the reciprocating motion is similar to balanced force technique that has been shown to maintain root canal curvature (Abou-Rass et al. 1980, Versiani et al. 2013). Twisted File Adaptive (TF Adaptive), a combined continuous rotation and reciprocating motion has been developed by SybronEndo (Orange, CA, USA) with three unique design features, namely R-phase heat treatment, twisting of the metal and special surface conditioning (Gambarini et al. 2012a,b). The manufacturer claims that this adaptive technology and twisted file design using R-phase treatment increases flexibility and allows the file to adjust to intra-canal torsional forces depending on the amount of pressure placed on the file (Gambarini et al. 2013). The aim of this study was to evaluate and compare the effect of different NiTi instrumentation techniques on canal volume, percentage of unshaped canal walls, canal transportation and centring ability when using Reciproc, WaveOne and TF Adaptive. High-definition micro-computed tomography (lCT) was used on extracted human mandibular molars with two separate mesial canals with acute curvature to evaluate the cutting ability of these systems. The null hypothesis was that no difference could be detected in the analysed parameters between the three preparation techniques.
Materials and methods Experimental teeth A total of twenty-four extracted human mandibular molars were selected from a pool of extracted teeth. Inclusion criteria stipulated that the tooth had a curved mesial root 25° < a < 35° (Schneider 1971), with two separate mesial canals, two separate apical foramina and a canal width at the apex of approximately size 15. Access cavities were prepared using a no. 4 high-speed round carbide bur (Dentsply Maillefer) with water spray. A size 15 K-file (Dentsply Maillefer) was placed into the canal until it was visible at the apical foramen and the working length (WL) established 0.5 mm short of this length. Teeth with apical diameters larger than size 15 were excluded from the study. A total of six small grooves were made on the external surface of the root using a HiDi 520 (Dentsply
2
International Endodontic Journal
Maillefer) round diamond bur and filled with composite (Z250; 3M ESPE, St Paul, MN, USA). These composite-filled grooves acted as reference points at levels 2.0, 4.0, 6.0, 8.0, 10.0 and 12.0 mm from the apex of the tooth for the superimposition of the lCT images obtained before and after instrumentation. Root canals (n = 48) were randomly assigned to one of the three experimental groups. Randomization was stratified to ensure that mesio-buccal and mesiolingual canals were distributed equally to each group consisting of 16 root canals. Group 1: Reciproc group (n = 16) The Reciproc R25 instrument size 25 and 0.08 taper over the first 3 mm was used in a reciprocating, slow in-and-out pecking motion according to the manufacturer’s instruction. The instrument R25 was operated in a reciprocating motion powered by a torque-limited electric motor (VDW Silver, Munich, Germany) using the preset adjustments. The instrument was introduced into the canal until resistance was felt and then moved in an apical direction using in-and-out pecking motion about 3 mm in amplitude with light apical pressure. After three pecking motions, the instrument was removed and cleaned, and the canal was irrigated with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. This protocol was repeated until WL was reached by the R25 instrument. Group 2: WaveOne group (n = 16) A primary reciprocating WaveOne file size 25 and 0.08 taper was used in a reciprocating, slow in-andout pecking motion according to the manufacturer’s instructions. The WaveOne instrument was operated in a reciprocating motion powered by a torque-limited electric motor (VDW Silver) using the manufacturer configuration setup. The instrument was introduced into the canal until resistance was felt and moved in an apical direction using in-and-out pecking motion about 3 mm in amplitude with light apical pressure. After three pecking motions, the instrument was removed and cleaned, and the canal was irrigated with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. This protocol was repeated until WL was reached by the R25 instrument. Group 3: TF Adaptive group (n = 16) Twisted File Adaptive instruments were operated with the Elements Adaptive Motion Technology:
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
1. The shaping procedure commenced with TFA size 25 and 0.08 taper. The coronal 1/3 or 2/3 of the root canal was shaped if passive penetration was possible. 2. TFA size 25 and 0.06 taper was inserted and used up to 2 mm short of WL. 3. Shaping continued with 0.04 taper size 25 instrument to the WL. 4. TFA size 25, 0.06 taper was taken to WL. 5. A 0.08 taper size 25 instrument was taken to WL. Canals were irrigated between instruments with 3 mL of a 5.25% NaOCl. Patency of the canal was checked by taking a size 15 K-type file to the WL. All groups After instrumentation, all root canals were irrigated with 3 mL of 5.25% NaOCl. A disposable syringe was used on which an Endo-Eze (Ultradent, South Jordan, UT, USA) irrigator tip was mounted. Glyde (Dentsply Maillefer) was used as a lubricant during instrumentation and when root canal instrumentation was completed 1 mL of 15% EDTA (Wizard; Rehber Kimya San., Istanbul, Turkey) was applied for 1 min and the canals flushed again with 3 mL of NaOCl. Each instrument was changed after three canals. Consequently, the final apical preparation resulting was standardized to size 25, 0.08 taper for all groups.
lCT scanning procedures and evaluation Before preparation and scanning, each experimental tooth was mounted on scanning electron microscopy carriers (014001-T; Bal-Tec AG, Balzers, Liechtenstein) to allow exact repositioning in the scanning system. Although the mounting device ensured
almost exact repositioning of the specimens, superimposition was further calculated with newly developed software (IPL Register 1.01; Scanco Medical, Br€ uttisellen, Switzerland), as previously reported by Paque et al. (2009). The composite-filled grooves were also used as reference points to superimpose the pre- and postoperative images. The final exact superimposition of the teeth before and after preparation was with a precision better than one voxel. Specimens were scanned initially and after root canal preparation at 140 kV and 200 lA with an isotropic resolution of 20 lm by using a commercially available lCT system (VTomeX, Wunstorf, Germany). All the scans were reoriented with respect to the x-, y- and z-axes using the imaging software MicroView (GE Pre-clinical Imaging, General Electric, London, UK). The volume of root canals and the surface area were evaluated in the apical, middle and coronal third of the canals using specially developed software (IPL V5.06B; Scanco Medical). The region of interest was selected extending from the floor of the pulp chamber to the apex of the roots. The apical, middle and coronal third regions of the canals were determined by calculating the number of cross-sectional slices from the apex of the tooth to the floor of the pulp chamber and then dividing by three. The resulting colour-coded root canal models (green indicates preoperative and red indicates postoperative canal surfaces) enabled quantitative comparison of the matched root canals before and after shaping (Paque et al. 2011, Fig. 1).
Measurement of canal volume and surface area Increases in canal volume and surface areas (i.e. amount of dentine removal) were calculated by
Figure 1 Representative example of pre- (green) and postoperative (red) micro-CT images. Green area is unprepared; red area is prepared.
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
International Endodontic Journal
3
Canal preparation assessed by micro-CT Gergi et al.
subtracting the scores for the treated canals from those recorded for the untreated counterparts. Matched images of the surface areas of the canals before and after preparation were examined to evaluate the amount of noninstrumented canal wall surface. This parameter was expressed as a percentage of the number of static voxel surface to the total number of surface voxels. The software counts a surface voxel as belonging to any given structure when the full voxel belongs to it. Therefore, to be counted as instrumented, at least one full voxel (i.e. 20 lm) had to be registered as removed from the preoperative canal model after superimposition (Stern et al. 2012). The pre- and post-instrumentation scans were superimposed to determine canal transportation and centring ability in the mesio-distal direction.
Evaluation of canal transportation To compare the degree of canal transportation, the technique developed by Gambill et al. (1996) was used. Using the 3D viewer and analysis software, MicroView, two-dimensional cross-sectional images of the teeth were produced. Transportation was evaluated by two operators at six different equidistant levels, predetermined with the line measuring tool of the MicroView software (GE Pre-clinical Imaging): two equidistant levels in the apical third, two equidistant levels in the mid-third and two equidistant levels in the coronal third. The examiners were trained and calibrated prior to measuring the experimental volume. The dimensions were determined by measuring the shortest distance from the edge of the uninstrumented canal to the edge of the tooth in both mesial and distal directions and then compared with the values measured from the prepared canals. The measurements of the distance of the points of interest were
taken with the line measuring tool of the MicroView software and averaged for each level. The following formula was used for the calculation of transportation: jða1 a2 Þ ðb1 b2 Þj where a1 is the shortest distance from the mesial edge of the curved root to the mesial edge of the uninstrumented canal; b1 is the shortest distance from distal (furcation) edge of the curved root to the distal edge of the uninstrumented canal; a2 is the shortest distance from the mesial edge of the curved root to the mesial edge of the instrumented canal; b2 is the shortest distance from distal (furcation) edge of the curved root to the distal edge of the instrumented canal (Fig. 2). According to this formula, a result of ‘0’ indicates no canal transportation. A result other than ‘0’ means that transportation had occurred.
Evaluation of centring ability According to Gambill et al. (1996), ‘the mean centring ratio’ indicates the ability of the instrument to stay centred in the canal. This ratio was calculated for each section using the following ratio: ða1 a2 Þ ðb1 b2 Þ or ðb1 b2 Þ ða1 a2 Þ If these numbers are not equal, the lower figure is considered as the numerator of the ratio. According to this formula, a result of ‘1’ indicates perfect centring.
Data presentation and statistical analysis The normality of the variable distribution in each group was verified using Kolmogorov–Smirnov tests.
Figure 2 Superimposed micro-CT images of the pre- and postoperative images. a1 = shortest distance from the mesial aspect of the root to the periphery of the uninstrumented canal. a2 = shortest distance from the mesial aspect of the root to the periphery of the prepared canal. b1 = shortest distance from the distal aspect of the root to the periphery of the uninstrumented canal. b2 = shortest distance from the distal aspect of the root to the periphery of the prepared canal.
4
International Endodontic Journal
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
One-way analysis of variance was used to test the comparability amongst groups concerning preoperative root canal volumes, preoperative canal angles and radius. One-way analysis of variance followed by post hoc tests Tukey’s Honestly Significant Different test (HSD) was conducted to explore a significant difference in mean dentine removal and in mean percentage of noninstrumented canals between the three shaping procedures: Reciproc, WaveOne and TF Adaptive in the apical third and in the entire root canal. The level of significance was set at a = 0.05. One-Sample t-test was conducted to determine whether the mean dentine removal and if the mean percentage of noninstrumented root canals were significantly different from 0. One-way analysis of variance followed by Tukey HSD test multiple comparisons was conducted to look at a significant difference in mean degree of canal transportation and in centring ratio between the three shaping procedure in each section of the root canal, and along the entire root canal. Onesample t-tests were conducted to find out if the mean degree of canal transportation was significantly different from 0. The level of significance was set at a = 0.05. One-sample t-tests were conducted to determine whether the mean centring ratio in each canal section and in each shape procedure was significantly different from 1 or 0. The level of significance was set at a = 0.05.
Results Preoperatively, there were no significant differences regarding root canal curvature and volume amongst experimental groups (P > 0.05).
Dentine removal along the entire canal The mean dentine removal along the entire canal was significantly different amongst groups (P = 0.013 and was significantly higher with the Reciproc system. No significant difference was found between WaveOne and TF Adaptive (P = 0.644; Table 1).
Dentine removal in the apical third The mean dentine removal in the apical third was significantly different amongst groups (P < 0.0001 and was significantly higher with the Reciproc
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Table 1 Amount of dentine removal (mean SD) in the apical third and in the entire root canal Dentine removal (mm3) In the entire canal Twisted File Adaptive Reciproc WaveOne In the apical third TF Adaptive Reciproc WaveOne
n
Mean
SD
Minimum
Maximum
16
1.07a
0.60
0.13
2.87
16 16
1.61b 0.84a
0.95 0.62
0.23 0.05
3.28 2.14
16 16 16
0.07a 0.19b 0.08a
0.04 0.10 0.06
0.01 0.03 0.01
0.15 0.35 0.21
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
system. No significant difference was found between WaveOne and TF Adaptive (P = 0.932; Table 1).
Noninstrumented surface along the entire canal The mean percentage of noninstrumented surface along the entire canal was significantly different amongst groups (P = 0.021 and was significantly lower with Reciproc. No significant difference was found between WaveOne and TF Adaptive (P = 0.483; Table 2, Fig. 3).
Noninstrumented surface in the apical third The mean percentage of noninstrumented surface in the apical third was significantly different amongst groups (P = 0.044) and was significantly lower with Reciproc. No significant difference was found between WaveOne and TF Adaptive (P = 0.692; Table 2).
Table 2 Percentage of noninstrumented surface area (mean SD) in the apical third and in the entire root canal Percentage
n
In the entire canal Twisted File 16 Adaptive Reciproc 16 WaveOne 16 In the third apical TF Adaptive 16 Reciproc 16 WaveOne 16
Mean
SD
Minimum
Maximum
28.77a
18.65
5.10
66.50
20.55b 35.31a
10.27 19.13
1.30 10.25
32.30 67.60
35.48a 25.00b 40.30a
17.03 18.59 16.55
7.70 0.90 16.40
67.30 56.90 76.40
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
International Endodontic Journal
5
Canal preparation assessed by micro-CT Gergi et al.
Canal transportation
Figure 3 Representative three-dimensional example of mesial canals in mandibular molar, showing noninstrumented surface areas (dark blue).
Surface area increase
Centring ratio
Mean increase in surface area within the apical third along the entire root canal was significantly higher with Reciproc (P < 0.001; ANOVA). No significant difference was found with WaveOne and TF Adaptive (P = 0.910; Table 3).
In each section of the root canal, there was a significant difference in mean centring ratio between the three shaping techniques (P < 0.0001). In the cervical section of the root canal, the mean centring ratio was significantly higher with TF Adaptive
Table 3 Surface area changes (mean SD) in the apical
third and in the entire root canal Surface area (mm2)
n
In the entire canal Twisted File 16 Adaptive Reciproc 16 WaveOne 16 In the apical third TF Adaptive 16 Reciproc 16 WaveOne 16
Mean
SD
Minimum
Maximum
Table 4 Absolute values of mean canal transportation (mm SD) for the coronal, middle, and apical thirds after preparation with TF Adaptive, Reciproc and WaveOne Mean canal transportation Twisted File Adaptive
a
13.45
5.10
36.30
46.12b 38.22a
16.23 14.23
1.30 10.25
22.10 32.60
Reciproc
25.26a 39.00b 28.10a
13.00 17.43 18.51
4.70 5.10 3.20
40.30 26.40 34.50
WaveOne
37.56
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
6
In each section of the root canal, there was a significant difference in mean degree of canal transportation between the three shaping techniques (P < 0.0001). In the cervical third, the transportation was significantly less with TF Adaptive (P < 0.0001). No significance difference was found between Reciproc and Wave One (P = 0.59). In the middle third, transportation was significantly less with TF Adaptive (P < 0.0001) followed by WaveOne and Reciproc (Table 4). In the apical third, the mean degree of canal transportation was significantly less with TF Adaptive (P < 0.0001), followed by WaveOne (P < 0.0001) and highest with the Reciproc system (P < 0.0001) (Table 4). The mean degree of canal transportation was significantly lower with TF Adaptive (P < 0.0001) followed by WaveOne and highest with Reciproc. In each section of the root canal, and with each shaping procedure, the mean degree of canal transportation was significantly different from 0 (P < 0.0001). TF Adaptive instruments had the least amount of root canal transportation with a significant difference when compared with Reciproc and WaveOne.
International Endodontic Journal
N
Level
16 16 16 16 16 16 16 16 16
Coronal Middle Apical Coronal Middle Apical Coronal Middle Apical
Mean SD 0.02 0.02 0.02 0.05 0.06 0.07 0.05 0.04 0.04
0.07a 0.06a 0.04a 0.09b 0.08c 0.07c 0.10b 0.09d 0.08d
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
(P < 0.0001). There was no significant difference between Reciproc and WaveOne (P = 0.329). In the middle and apical sections of the root canal, the mean centring ratio was significantly higher with the TF Adaptive system (P < 0.0001) followed by WaveOne and was minimal with Reciproc (P < 0.05; Table 5).
Discussion In the current study, the shaping ability of two reciprocating single-file systems (Reciproc and WaveOne) and one combined continuous/reciprocation motion (TF Adaptive) was evaluated by lCT. The experimental design had several variables: the manufacturing process, the number of files used and movement kinematic. It is not possible to isolate the influence of each variable on the results. The Reciproc and the WaveOne files alternate between clockwise (CW) and counter-clockwise rotation during the shaping procedure. According to the manufacturer, the fact that the rotation in the cutting direction is larger than the reverse rotation helps the reciprocating files to progress along the canal path, whilst respecting root canal anatomy. The reciprocating movement relieves stress on the instrument and reduces the risk of cyclic fatigue caused by tension and compression (B€ urklein et al. 2011). The newly introduced TFA system uses an existing file set called Twisted Files in conjunction with the new Elements Motor featuring Adaptive Motion. According to the manufacturer, the Adaptive Motion relies on a patented algorithm that changes the motion of the file based on the applied load. This
Table 5 Mean and standard deviation (SD) of the centring ratio (mm SD) for the coronal, middle and apical thirds after preparation with TF Adaptive, Reciproc and WaveOne Mean centring ratio Twisted File Adaptive Reciproc
WaveOne
n
Level
16 16 16 16 16 16 16 16 16
Cervical Median Apical Cervical Median Apical Cervical Median Apical
Mean SD 0.93 0.93 0.94 0.54 0.58 0.52 0.618 0.643 0.610
0.05a 0.06a 0.05a 0.12b 0.18c 0.089c 0.074b 0.072d 0.062d
Different superscript letter indicates statistically significant difference between groups (P < 0.05).
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
patented algorithm ‘adapts’ to canal conditions based on the amount of pressure on the file. When the file is not loaded or lightly loaded, it will rotate continuously in a CW direction with no backward movement. When the file is loaded, reciprocation angles vary: 370° forward and 20° to 50° backwards, based on file load. In the present study, mesial roots with acute curves of mandibular molars were selected because these contain canals that are often narrow and curved in two planes increasing the level of instrumentation difficulty (Berutti & Fedon 1992). The focus of the study was clearly on the quality of the final canal shape. However, the limitations of the current study are clear; extracted human teeth were instrumented in a set-up that differs from the clinical situation. Patient comfort and other strictly clinical outcomes could thus not be investigated. Furthermore, only one experienced operator performed the operative procedures, rendering the experiment better standardized. However, conclusions cannot directly be extrapolated to the average potential user of the techniques under investigation. The effect of canal instrumentation was analysed quantitatively by using a set of parameters including canal volume and un-instrumented canal surface area. All these results are mean values over the entire canal length and over the apical third, measured three-dimensionally using lCT. Accuracy and reproducibility of the lCT system have been verified previously, and it is accepted as an important scientific tool for the effect analysis of different shaping techniques (Gambarini et al. 2012a,b). Electron microscopy carriers and the use of newly developed software (IPL Register 1.01; Scanco Medical), as previously reported by Paque et al. (2011) allowed exact repositioning and superimposition in the scanning system with a precision better than one voxel. Root canal instrumentation resulted in significant gains in canal volumes and surface areas. Overall, the highest mean increase of the parameters was observed with the Reciproc group when compared with WaveOne and TF Adaptive. The cutting ability of root canal instruments is a complex interrelationship of different parameters such as the cross-sectional design, helical and rake angle, metallurgical properties, surface treatments of the instrument and movement kinematics (Capar et al. 2013). Canal volume is a variable used to analyse the effects of canal instrumentation on dentine removal (Peters et al. 2010, Berutti et al. 2012a,b).
International Endodontic Journal
7
Canal preparation assessed by micro-CT Gergi et al.
Over-instrumentation of the root canal could result in excessive thinning of the root. In the present study, root canal instrumentation resulted in an increase in canal volume and surface area with Reciproc showing a greater amount of removed dentine than WaveOne and TF Adaptive. None of the three NiTi systems was able to instrument completely the entire root canal wall; approximately 20–35% of the canal surface area was found uninstrumented in the three groups after preparation, which is consistent with previous studies (Paque et al. 2011, Versiani et al. 2013). These untouched areas may harbour unaffected residual bacteria biofilms and serve as a potential cause of persistent infection and poor treatment outcome (Alves et al. 2011, Dietrich et al. 2012). To date, there are no studies comparing root canal transportation of TF Adaptive to reciprocating NiTi instruments Reciproc and WaveOne. With similar apical preparation diameter, the results revealed that TF Adaptive files produced significantly less transportation and a better centring ratio followed by WaveOne and by Reciproc system. The Adaptive Motion combined with the flexibility of the TF files may explain the shaping results obtained with the TF Adaptive system (Zhao et al. 2013). Additionally, the use of the multiple file TF Adaptive system with smaller tapered instruments reaching WL before instrument size 25 taper 0.08 can also be an important factor in reducing the amount of transportation (Gergi et al. 2010, Marzouk & Ghoneim 2013). Berutti et al. (2011) revealed a significant decrease in canal length mainly because of straightening of root canal curves after instrumentation with the WaveOne single-file primary reciprocating file (size 25 taper 8%). Since WaveOne and Reciproc instruments are used without first performing preliminary coronal enlargement, this may result in a greater engagement of the flutes and may produce consequently more torque and/or applied pressure on the file resulting in a higher incidence of canal transportation (Pak & White 2011). Canal transportation was higher with Reciproc compared with WaveOne, especially in the apical third. Despite the Reciproc and WaveOne instruments having similarities (same alloy, reciprocation movement and tip size), their different cross-sectional designs may explain the greater cutting ability and canal transportation of Reciproc (Versiani et al. 2013). Reciproc size 25 taper 0.08 has a sharp double-cutting edge S-shaped geometry, whereas WaveOne is characterized by a modified triangular cross section with radial lands at the tip and a convex triangular cross section in the
8
International Endodontic Journal
middle and coronal portion of the instrument. The WaveOne modified cross section results in lower cutting efficiency and less chip space (You et al. 2011). Coronal enlargement, canal scouting and preliminary creation of a glide path are fundamental for the safer use of NiTi rotary instrumentation. A recent study has shown that the WaveOne Primary instrument produced less modification in the canal curvature if used with a glide path, suggesting that the presence of a larger canal improves the performance of the instrument (Berutti et al. 2012a,b).
Conclusion Within the limits of this study, the null hypothesis that there is no difference between Reciproc, WaveOne and TF Adaptive in the preparation of mesiobuccal and mesio-lingual root canals of mandibular molars was rejected. The TF Adaptive system maintained the original canal anatomy with less modification of the canal curvature compared with the WaveOne and Reciproc system. Overall instrumentation led to enlarged canal shapes with no evidence of preparation errors; however, none of the three NiTi systems was able to shape completely the root canal.
References Abou-Rass M, Frank AL, Glick DH (1980) The anticurvature filing method to prepare the curved root canal. Journal of the American Dental Association 101, 792–4. Alves FR, Almeida BM, Neves MA, Moreno JO, R^ ocßas IN, Siqueira JF Jr (2011) Disinfecting oval shaped root canals: effectiveness of different supplementary approaches. Journal of Endodontics 37, 496–501. Berutti E, Fedon G (1992) Thickness of cementum dentin/ dentin in mesial roots of mandibular first molars. Journal of Endodontics 18, 545–8. Berutti E, Chiandussi G, Paolino DS et al. (2011) Effect of canal length and curvature on working length alteration with WaveOne reciprocating files. Journal of Endodontics 37, 1687–90. Berutti E, Chiandussi G, Paolino DS et al. (2012a) Canal shaping with WaveOne Primary reciprocating files and ProTaper system: a comparative study. Journal of Endodontics 38, 505–9. Berutti E, Paolino DS, Chiandussi G et al. (2012b) Root canal anatomy preservation of WaveOne reciprocating files with or without glide path. Journal of Endodontics 38, 101–4. B€ urklein S, Hinshitza K, Dammashke T, Sch€ afer E (2011) Shaping ability and cleaning effectiveness of two single-file systems in severely curved root canals of extracted teeth:
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
Gergi et al. Canal preparation assessed by micro-CT
Reciproc and WaveOne versus Mtwo and ProTaper. International Endodontic Journal 45, 449–61. Capar ID, Ertas H, Ok E, Arslan H, Ertas ET (2013) Comparative study of different novel nickel-titanium rotary systems for root canal preparation in severely curved root canals. Journal of Endodontics 10, 1–5. Dietrich MA, Kirkpatrick TC, Yaccino JM (2012) In vitro canal and isthmus debris removal of the self-adjusting file, k3 and WaveOne files in the mesial root of human mandibular molars. Journal of Endodontics 38, 1140–4. Gambarini G, Gergi R, Naaman A, Osta N, Al Sudani D (2012a) Cyclic fatigue of twisted file rotary NiTi instruments used in reciprocating motion. International Endodontic Journal 45, 802–6. Gambarini G, Rubini AG, Al Sudani D et al. (2012b) Influence of different angles of reciprocation on the cyclic fatigue of nickel-titanium endodontic instruments. Journal of Endodontics 38, 1408–11. Gambarini G, Testarelli L, De luca M et al. (2013) The influence of three different instrumentation techniques on the incidence of postoperative pain after endodontic treatment. Annali di Stomatologia e dell’Istituto Superiore di Odontoiatria 20, 152–5. Gambill JM, Alder M, del Rio CE (1996) Comparison of nickel-titanium and stainless steel hand-file instrumentation using computed tomography. Journal of Endodontics 22, 369–75. Gergi R, Rjeily JA, Sader J, Naaman A (2010) Comparison of canal transportation and centering ability of twisted files, Pathfile-ProTaper system, and stainless steel hand K-files by using computed tomography. Journal of Endodontics 36, 904–7. Marzouk AM, Ghoneim AG (2013) Computed tomographic evaluation of canal shape instrumented by different kine-
© 2014 International Endodontic Journal. Published by John Wiley & Sons Ltd
matics rotary nickel-titanium systems. Journal of Endodontics 39, 906–9. Pak JG, White SN (2011) Pain prevalence and severity before, during and after root canal treatment: a systematic review. Journal of Endodontics 37, 427–38. Paque F, Laib A, Gautschi H, Zehnder M (2009) Hard-tissue debris accumulation analysis by high-resolution computed tomography scans. Journal of Endodontics 35, 1056–9. Paque F, Zehnder M, De-Deus G (2011) Microtomographybased comparison of reciprocating single-file F2 ProTaper technique versus rotary full sequence. Journal of Endodontics 37, 1394–7. Peters OA, Boessler C, Paque F (2010) Root canal preparation with a novel nickel titanioum instrument evaluated with micro-computed tomography; canal surface preppartion over time. Journal of Endodontics 36, 1068–72. Schneider SW (1971) A comparison of canal preparations in straight and curved root canals. Oral Surgery Oral Medicine Oral Pathology Oral Radiology Endodontology 32, 271–5. Stern S, Patel S, Foschi F et al. (2012) Changes in centering and shaping ability using three nickel-titanium instrumentation techniques analysed by micro-computed tomography (lCT). International Endodontic Journal 45, 514–23. Versiani MA, Leoni GB, Steier L et al. (2013) Micro-computed tomography study of oval-shaped canals prepared with the Self-adjusting File, Reciproc, WaveOne, and ProTaper Universal systems. Journal of Endodontics 39, 1060–6. You SY, Kim HC, Bae KH et al. (2011) Shaping ability of reciprocating motion in curved root canals: a comparative study with micro-computed tomography. Journal of Endodontics 37, 1296–300. Zhao D, Peng B, Haapsalo M (2013) Micro-computed tomograohy evaluation of the preparation of mesiobuccal root canals in maxillary first molars with Hyflex CM, Twisted Files and K3 instruments. Journal of Endodontics 39, 385–8.
International Endodontic Journal
9
