doi:10.1111/iej.

13163

Evaluation of two shaping systems and two sonic

irrigation devices in removing root canal filling
material from distal roots of mandibular molars
assessed by micro CT

M. K. Kaloustian1 , W. Nehme1 , C. El Hachem2, C. Zogheib1 , N. Ghosn3,

J. P. Mallet4, F. Diemer4 & A. Naaman1
1
Department of Endodontics; 2Department of Pediatric Dentistry; 3Department of Oral and Maxillofacial Radiology, Faculty of
Dentistry, Saint Joseph University, Beirut, Lebanon; and 4Facult!e de Chirurgie Dentaire, CHU de Toulouse – Institut Cl!ement
Ader (laboratoire), Toulouse, France

Abstract groups, 2Shape was followed subsequently by

MM1500 and Eddy; in the third and fourth groups,
Kaloustian MK, Nehme W, El Hachem C, Zogheib
Reciproc was followed by MM1500 and Eddy. A third
C, Ghosn N, Mallet JP, Diemer F, Naaman A.
micro-CT was taken to compare the remaining root
Evaluation of two shaping systems and two sonic irrigation
filling material in all groups. Wilcoxon’s signed rank
devices in removing root canal filling material from distal
tests, Mann–Whitney and Kruskal–Wallis tests were
roots of mandibular molars assessed by micro CT.
used for statistical analysis.
International Endodontic Journal.
Results No significant difference was found for the
Aim To compare two preparation systems and two volume of filling material removed between the Reci-
sonic irrigation devices during the removal of root fill- proc and 2Shape in the entire canal (P = 0.355). The
ing material from oval distal canals of extracted volume dropped significantly from its initial value
mandibular molars. after removing the bulk of the root filling by 95.8%
Methodology The distal canals in 40 extracted (from 4.71 to 0.22 mm3) with the 2Shape
mandibular molars were shaped using the ProTaper (P < 0.001) and by 94.0% (from 5.05 to 0.33 mm3)
Next system (Dentslpy Sirona, Ballaigues, Switzer- with the Reciproc (P < 0.001). Sonic activation signif-
land), filled with Gutta Percha X2 (Dentsply Sirona), icantly decreased the residual volume of filling mate-
along with AH Plus sealer (Dentsply De Trey, Kon- rial remnants by 3.21% (P = 0.013) in the first
stanz, Germany) and randomly divided into two group, 1.38% (P = 0.012) in the second group,
groups (n = 20) according to volume of initial filling, 1.83% (P = 0.008) in the third group and 1.83%
preparation diameter and working length. One group (P = 0.012) in the fourth group. At the end, the per-
was retreated using the Reciproc system (VDW, centage of residual material was not significantly dif-
Munich, Germany), and the other using the 2Shape ferent among the groups in the entire canal
system (Micro-Mega, Besanc!on, France). A micro-CT (P = 0.163).
scan was taken after the initial root filling and after Conclusion In the distal oval canals of extracted
retreatment to evaluate the volume of filling material mandibular molar teeth, there was no significant dif-
remnants. The teeth were divided into four groups to ference between the 2Shape and Reciproc systems in
test the supplementary effect of two sonic irrigation removing gutta-percha/sealer. Sonic activation with
devices on removing filling material: Eddy (VDW) and MM1500 and Eddy significantly improved filling
MM1500 (Micro-Mega). In the first and second material removal.

Correspondence: Marc Krikor Kaloustian, Department of Endodontics, Faculty of Dentistry, Saint Joseph University, Campus des
sciences m!edicales, Rue de Damas, B.P. 11-5076 - Riad El Solh, Beyrouth 1107 2180, Lebanon (e-mail: mkaloustian75@
gmail.com).

© 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd International Endodontic Journal 1
 Removal of filling material using different systems Kaloustian et al.

Keywords: 2Shape, micro CT, Reciproc, retreat- Received 4 February 2019; accepted 22 May 2019
ment, sonic activation.

in root canal retreatment has not yet been docu-

Introduction
mented.
Reciproc instruments (VDW), made of M wire, possess The aim of this study was to compare the efficacy
a colon cross-section and a regressive taper starting of the Reciproc and 2Shape systems in the removal of
with 8% for R25 and 6% for R40 (Ye & Gao 2012). GP and sealer from oval distal canals of mandibular
Originally designed for shaping procedures with a molars and, as a secondary objective, to evaluate the
reciprocating movement, these files have also been additional cleaning effect of two sonic devices,
used in root canal retreatment (Crozeta et al. 2016). MM1500 and Eddy. The capacity of these systems to
Some studies have suggested that the Reciproc system remove remnants of root filling was assessed using
was equally effective as rotary systems in removing high-resolution micro-computed tomography (micro-
root filling material (Zuolo et al. 2013, Helvacioglu- CT) scans.
Yigit et al. 2014). The first null hypothesis is that there is no signifi-
The 2Shape system (Micro-Mega) is also designed cant difference between the 2shape and the Reciproc
for primary root canal treatment, but in continuous in removing GP and sealer from the distal roots of
rotation. The system comprises two shaping files, TS1 mandibular molars. The second null hypothesis is
size 25, .04 taper and TS2 size 25, .06 taper which that sonic irrigation (SI) does not improve the
are sufficient in almost 80% of cases, and two finish- removal of the filling material remnants.
ing files, F35 size 35, .06 taper and F40 size 40, .04
taper. The 2Shape system has undergone a thermo-
Materials and methods
mechanical proprietary process not disclosed by the
manufacturer. The files have a special cross-section
Sample selection
with a modified triple helix blade. One of the three
blades is off-centred and is 0.06 mm shorter than the After the approval of the institutional ethical commit-
two others. This will confer a larger space for the tee (USJ-2017-55), one hundred mandibular molars,
shaved debris and reduce the stress on the files extracted for reasons independent from this study,
(http://www.micro-mega.com). The capacity of the were first cleansed with an ultrasonic tip (2S, Satelec
2Shape system to remove filling material from oval Acteon Group, Merignac, France) and then stored in
canals with a brushing motion has not yet been formocresol 0.1%.
tested. Using a dental operating microscope (Zeiss Extaro
No root canal preparation system is able to remove 300, Oberkochen, Germany) with 916 magnification,
root filling material completely (Ma et al. 2012, Rios the teeth were examined, and the inclusion criterion
Mde et al. 2014, Yilmaz et al. 2018), and additional was molars with a single distal straight oval canal.
procedures are recommended to enhance the removal Cone beam computed tomography (Newtom VGI, Ver-
of remnants after instrumentation (Martins et al. ona, Italy) (CBCT) was performed, and the canals
2017, Silveira et al. 2018). Ultrasonic activation has were classified as oval when the major buccolingual
been proposed to improve the removal of residual fill- diameter of the canal in mm on cross-sections was
ing materials (Jiang et al. 2016). Eddy (VDW) is a rel- two or more times wider than that of the major
atively new noncutting plastic tip mounted on an air mesiodistal diameter throughout the coronal two-
scaler that operates at 6000 Hz to produce sonic agi- thirds of the root, 5 mm from the apex (Fig. 1).
tation. MM1500 Sonic Air (Micro-Mega) is another The exclusion criteria consisted of teeth with cracks
air-driven hand-piece coupled to the airlines of dental or external resorption and teeth with previously trea-
units, with an adjustable frequency ranging from zero ted canals, pulp calcification or internal resorption.
to 1500 Hz. The device was coupled with a stainless Forty molars met the inclusion criterion (n = 40).
steel prototype tip designed specifically for this study. Access cavity preparation, root canal shaping, filling
The efficiency of the new prototype compared to Eddy and secondary treatment procedures were performed

2 International Endodontic Journal © 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd
 Kaloustian et al. Removal of filling material using different systems

Figure 1 Example of a cross-section in the coronal and middle thirds to determine whether the canal was oval.

by a specialist in Endodontics using an operating Jordan, UT, USA). The smear layer was removed with
microscope (Zeiss Extaro 300). 3 mL of 17% EDTA followed by a final rinse of 3 mL
All crowns were sectioned identically with a dia- of 6% NaOCL. Each instrument was used to prepare
mond disc (Kerr Dental, Bioggio, Switzerland) until a one canal.
17 mm root length was achieved. The occlusal Canals were dried using sterile size X2 absorbent
ground surface of the crowns was sealed with Teflon points (Dentsply Sirona) and filled with X2 GP points
tape and Cavit (3M ESPE, Seefeld, Germany) and fixed (Dentsply Sirona), AH Plus sealer (Dentsply De Trey)
on a 2 cm square sheet of plexiglass with a 1 mm using the continuous wave vertical compaction tech-
thickness using hot glue. An access was created nique with a fine (F) 06 plugger (Sybron Dental Spe-
through the plexiglass using a high-speed carbide bur cialties, Orange, CA, USA). For backpacking, GP was
(Dentsply Sirona, York, PA, USA) under water cool- injected using the Obtura II with a 23G tip (Obtura
ant. Spartan Endodontics, Algonquin, IL, USA). The qual-
A custom-made silicone key was prepared because ity of the filling in terms of length and density was
the platform of the micro CT (EA2496, Hopkinton, verified by taking a buccolingual and a distomesial
Montrouge, France) was circular and could not fit the digital radiograph (Sopix, Satelec Acteon Group).
flat plexiglass in the same position. The silicone key A temporary restoration (Cavit, 3M ESPE, Seefeld,
moulding the platform from one side and the plexi- Germany) was placed in the access cavities. Teeth
glass from the other side offered a reproducible posi- were then incubated at 37 °C and fully saturated
tioning for later scans. humidity for 14 days to allow the endodontic sealers
to set.
Initial preparation and root canal filling
Pre-secondary treatment imaging
A size 10 K-file (Dentsply Sirona, Ballaigues, Switzer-
land) was used to ensure patency in all 40 distal root The micro-CT Platform (EA2496, Hopkinton, Mon-
canals. The working length (WL) was then deter- trouge, France) for tooth imaging was used to scan
mined with a size 15 K-file (Dentsply Sirona) that each distal root using a micro-CT scanner (Quantum
was 1 mm short of the apical foramen and checked FX, PerkinElmer Health Sciences, Hopkinton, MA,
with a digital radiograph (Sopix, Satelec Acteon USA). A 10 mm field of view was used to acquire 3D
Group). The ProTaper Next system (Dentsply Sirona) images with an isotropic resolution of 20 lm. The
was used to shape all the canals. X1 size 17, .06 settings were 160 kV, 90 mA and 360° scanning
taper and X2 size 25, .06 taper files were used rotation.
according to the manufacturer’s instructions in an in/
out and brushing motion with an amplitude of 3 mm
Secondary treatment
to the WL. A size 10 K-file was inserted after each file
to maintain apical patency, and the canal was irri- A block randomization method was used to random-
gated with 3 mL of 6% sodium hypochlorite (NaOCL) ize teeth into two groups with equal numbers. A
using a 30 G NaviTip needle (Ultradent, South block size of 4 was chosen, and possible balanced

© 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd International Endodontic Journal 3
 Removal of filling material using different systems Kaloustian et al.

combinations were with 11 for group 1 and 22 for All canals were irrigated with a total of 12 mL of
group 2 (1122, 1212, 1221, 2112, 2121, 2211). 6% NaOCL with a 30 G NaviTip needle (Ultradent).
Blocks were randomly chosen to determine the Then, 3 mL of 17% EDTA was applied inside the
assignment of all 40 teeth with 20 teeth in each canal for 1 minute, and another 3 mL of 6% NaOCL
group. was flushed as a final wash. A dental operating
To ensure groups were comparable, morphologic microscope (Zeiss Extaro 300) with 916 magnifica-
parameters (volume of initial filling, preparation diam- tion was used during the retreatment to evaluate the
eter, and working length) were compared using the absence of filling material inside the canals. If at the
ANOVA tests (P > 0.05) (Table 1). A single experi- end of the sequence, remnants were detected, the last
enced Endodontist performed secondary treatment file reaching the apical foramen was inserted again
procedures for all canals. with a brushing motion until all visible material was
eliminated (Schirrmeister et al. 2006, Kfir et al.
Group 1 2012). The retreatment procedure was considered
The canals in group 1 were prepared using TS2 size complete when the filling material was no longer evi-
25, .06 taper, F35 size 35, .06 taper and F40 size 40, dent on the file or on the canal walls when checked
.04 taper. The files were operated on an MM control with a dental operating microscope under 916 mag-
motor (Micro-Mega) at 300 rpm and 2.5 Ncm in a nification.
pecking and brushing motion with an amplitude of
3 mm. After three movements, the debris was
Postsecondary treatment imaging
removed from the instrument using a sterile gauze;
the instrument was then inspected to detect any dis- The roots were scanned once again in the micro-CT
tortion, and the procedure was repeated until the WL device with the same parameters after the retreatment
was reached for each instrument. procedure. The volume and percentage of residual fill-
ing material were calculated for all canals in the
Group 2 coronal, middle and apical thirds.
The canals in group 2 were prepared using R25 size
25, .08 taper and R40 size 40, .06 taper. The files
Supplementary approach using sonic irrigation (SI)
were used on a VDW Silver Reciproc motor (VDW) in
the All Reciproc Mode in a pecking and brushing A supplementary agitation technique was used to test
motion with an amplitude of 3 mm. After three two sonic irrigation (SI) devices. Canals in groups 1
movements, the debris was removed from the instru- and 2 were divided randomly using the same ran-
ment using a sterile gauze; the instrument was then domization technique into two sub groups (n = 10).
inspected to detect any distortion, and the procedure Group 1a: 2Shape system with the MM1500
was repeated until the WL was reached for each device.
instrument. Group 1b: 2Shape system with the Eddy device.
For all 40 canals, each set of instruments was used Group 2a: Reciproc system with the MM1500
to remove root filling material from two canals. device.
Group 2b: Reciproc system with the Eddy device.
The MM1500 device is usually used with either
Rispisonic! instruments to debride the coronal two-
Table 1 Morphologic parameters (volume of initial filling, thirds or Shapersonic! instruments for simultaneous
preparation diameter and working length) were compared debriding of the apical and coronal thirds (Dummer
using the ANOVA tests (P > 0.05) to ensure groups were
et al. 1993, Lumley 1997). In the present study, a
comparable
customized stainless steel prototype replaced the
2Shape Reciproc P Rispisonic! and Shapersonic! instruments to avoid
Volume of initial 4.718 ! 1.098 5.056 ! 1.436 0.409
canal shaping. The prototype had a 0.15 mm tip with
filling (mm3) a 2% taper and no cutting edges. According to the
Working length 16 16 manufacturers, the Eddy system has a tip size of
(mm) 0.2 mm but a nondisclosed taper. An endodontic
Preparation 0.25 0.25
gauge (Dentsply Sirona) was used to calculate the
diameter (mm)
diameter of Eddy at several levels. It was 0.2 mm at

4 International Endodontic Journal © 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd
 Kaloustian et al. Removal of filling material using different systems

the tip and 0.7 mm 10 mm from the tip, which GP and sealer before and after the retreatment and
implies an overall estimated continuous taper of 5% the volume of the material remnants before and after
over a length of 10 mm. SI. Mann–Whitney tests were applied for the compar-
The same irrigation protocol was applied for both ison of the percentage of the material remnants
devices with a 4 mm amplitude in-and-out move- between the two retreatment systems. Kruskal–Wallis
ments without touching canal walls. 3 mL of 6% tests were used to compare the percentage of material
NaOCL irrigation followed by 20 s of activation was remnants after using SI activation among the four
repeated 3 times at 1 mm from the WL. The canals groups.
were dried and irrigated with 3 mL of 17% EDTA fol-
lowed by 1 minute of activation and a final rinse with
Results
3 mL of 6% NaOCL.
In the entire distal canal, the volume of the filling
material dropped significantly, from its initial value
Post-SI imaging
after removing the bulk of the root filling by 95.8%
A final scan with the same settings was performed to (from 4.71 to 0.22 mm3) with the 2Shape system
assess the effect of the two additional SI systems on (P < 0.001) and by 94.0% (from 5.05 to 0.33 mm3)
GP/sealer removal. with the Reciproc system (P < 0.001). No significant
difference was found between the systems when the
entire canal was considered (P = 0.355).
Micro-CT analysis
In the retreated distal canal, sonic activation signifi-
3D images were reconstructed with Quantum FX cantly decreased the residual volume of filling mate-
micro-CT! software (March 2013, PerkinElmer rial by 3.21% (P = 0.013) for the 2Shape with
Health Sciences, Hopkinton, MA, USA). MATLAB! MM1500 group, 1.38% (P = 0.012) for the 2Shape
software (MATLAB 9.3, MathWorks, Natick, MA, with Eddy group, 1.83% (P = 0.008) for the Reciproc
USA) with an automatic rigid registration was used with MM1500 group and 1.83% (P = 0.012) for the
to align the three stages of acquisition for compari- Reciproc with Eddy group.
son. The hard tissue of the teeth, the background At the end of the retreatment and activation pro-
and the filling material remnants were segmented cess, the percentage of residual material was not sig-
using a global thresholding technique (Otsu 1979). nificantly different among the groups in the entire
The volumes were then binarized to visualize only canal (P = 0.163) (Fig. 2).
filling material remnants. The filling material was The mean volume and standard deviation (mm3) of
quantified in mm3 after canal filling and the two the initial material (IM), residual material after the
stages of the secondary treatment procedure (Michetti retreatment (RM1), residual material after the addi-
et al. 2017). The localization of the filling material tional cleaning methods (RM2) and the mean per-
remnants was determined for the coronal, middle and centage of the residual filling materials (%) after
apical thirds. The percentage of GP and sealer rem- applying the additional cleaning methods according
nants was then calculated using this method: A/ to the groups studied in all canal thirds are detailed
B 9 100 = Volume (%) of filling material remnants. in Table 2.
A is the postsecondary treatment volume of filling
material, and B is the preoperative volume of filling
Discussion
material.
In the present study, the oval distal canals of
mandibular molars were selected because they are
Statistical analysis
challenging for all mechanized systems for both the
SPSS (version 24.0, Chicago, IL, USA) was used to preparation of canals and the removal of filling mate-
analyse the data with the level of significance set at rial (Ma et al. 2012).
0.05 (P < 0.05). Kolmogorov–Smirnov tests were The micro-CT technique is a highly accurate and
used to assess the normality distribution of continu- nondestructive method for the evaluation of root
ous variables. Nonparametric tests were applied since canal fillings (Crozeta et al. 2016). This technique has
variables were not normally distributed. Wilcoxon’s also been used to evaluate root canal filling remnants
signed rank test was used to compare the volume of after root canal retreatment without destroying the

© 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd International Endodontic Journal 5
 Removal of filling material using different systems Kaloustian et al.

Figure 2 Reconstructed 3D micro-CT images for groups 1 a, 1 b, 2 a and 2 b. For each group, the initial material (IM), resid-
ual material (RM1) and residual material (RM2) after SI were determined.

6 International Endodontic Journal © 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd
 Kaloustian et al. Removal of filling material using different systems

samples (Roggendorf et al. 2010, Da Rosa et al.

14.011

16.889
Table 2 The mean volume and standard deviation (mm3) of the initial material (IM), residual material after the retreatment (RM1), residual material after the additional clean-

8.416
1.517
4.615

8.134
0.854
4.323
2015, Jiang et al. 2016). This kind of analysis can-
ing methods (RM2) and the mean percentage of the residual filling material (%) after applying the additional cleaning methods according to the groups studied in all canal

%
not be achieved with clearing or sectioning tech-

%
!
!
!
!

!
!
!
!
7.778
3.625
0.484
2.302

5.601
1.089
13.927

4.513
niques, while the same image quality cannot be
obtained with other available imaging technologies,
such as periapical radiographs or cone beam com-
puted tomography scans (Nielsen et al. 1995).
0.086
0.111
0.035
0.211

Reciproc system + Eddy (n = 10)

2Shape system + Eddy (n = 10)

0.157
0.245
0.021
0.334
In the present study, two types of motion were
RM2

RM2
!
!
!
!

tested (rotary, reciprocating). The two shaping sys-

!
!
!
!
0.048
0.053
0.011
0.113

0.118
0.128
0.027
0.274
tems reduced significantly the amount of root filling
material, which corroborate the results of similar
studies comparing rotational and reciprocating sys-
tems (Zuolo et al. 2013, Helvacioglu-Yigit et al.
0.109
0.131
0.104
0.233

0.214
0.243
0.043
0.412

2014). However, no significant difference occurred

RM1

RM1
!
!
!
!

between the rotary and reciprocating files. Both sys-

!
!
!
!
0.070
0.094
0.046
0.181

0.134
0.182
0.054
0.370

tems were unable to completely eliminate the filling

material during retreatment, which is in accordance
with previous results (Ma et al. 2012, Martins et al.
2017, Silveira et al. 2018). Therefore, the first null
0.199
0.427
0.427
0.941

0.249
0.629
0.839
1.525

hypothesis was accepted with no significant differ-

IM

!
!
!
!

IM

ence between both systems.

!
!
!
!
0.597
1.634
2.713
4.944

0.690
1.783
2.763
5.249

The results of the present study are in agreement

with the results reported by others (Zuolo et al.
2013, R€ odig et al. 2014, Da Rosa et al. 2015) but
different from those obtained by Bernardes et al.
14.858
2.282
1.319
3.111

15.288
3.530
3.868
4.220

(2016), who found that R50 was associated with

less retained material than PTUR and PTU. The
%

!
!
!
!

!
!
!
!
15.240
1.173
0.624
2.389

results are also different from the only published

7.494
2.878
2.202
3.733

paper comparing the 2Shape and Reciproc systems,

in which the 2Shape system outperformed the Reci-
proc system in the removal of filling material
Reciproc system + MM1500 (n = 10)
2Shape system + MM1500 (n = 10)

0.085
0.033
0.036
0.149

0.226
0.064
0.115
0.258

(Kaloustian et al. 2019). The difference in results

RM2

RM2

could be due to different study parameters, such as

!
!
!
!

!
!
!
!
0.081
0.018
0.017
0.115

0.091
0.052
0.065
0.208

the cross-section of the samples and the number

and size of the files used for retreatment. Oval distal
canals were used in the present study, while more
circular mesial canals of mandibular molars were
0.096
0.200
0.084
0.342

0.278
0.134
0.146
0.416

used in the study by Kaloustian et al. (2019). Oval

RM1

RM1

distal canals of mandibular molars were also used in

!
!
!
!

!
!
!
!
0.092
0.125
0.042
0.259

0.110
0.109
0.078
0.297

the study by Solomonov et al. (2012) to compare

the ProFile and SAF to the ProTaper in the removal
of filling material.
Furthermore, in the present investigation, two or
0.187
0.474
0.702
1.245

0.402
0.428
0.720
1.394

more large files were used from each system, with

size 40, .04 taper as the final finishing file, instead
IM

IM
!
!
!
!

!
!
!
!
0.496
1.346
2.651
4.492

0.652
1.542
2.670
4.863

of small and single files, such as the R25 size 25,

.08 taper and TS2 size 25, .06 taper, as reported in
the study by Kaloustian et al. (2019). The increase
in efficacy with the Reciproc system in this study
Coronal

Coronal
Middle

Middle
Apical

Apical
thirds

could be explained by the results of previous investi-

Total

Total

gations showing that the use of larger reciprocating

© 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd International Endodontic Journal 7
 Removal of filling material using different systems Kaloustian et al.

files will increase the amount of material removed force and amount of streaming depend on the free-
(Bernardes et al. 2016, Crozeta et al. 2016). Never- dom of file movement and the period of time the file
theless, these conclusions were contested by Crozeta is used in the canal (Krell et al. 1988). In the pre-
et al. (2016) whom found that the Reciproc R50 left sent study, the time allocated for activation was the
more residual material than the TF adaptive and Pro- same for both systems (20 s repeated 3 times). The
Taper Universal Retreatment combined with ProTaper amount of movement was greater for Eddy, because
Universal F2, F3, F4 and F5 files. Better results from of its higher frequency. Nonetheless, the results were
the rotating systems, according to the authors, were similar. A smaller space could prevent the free
related to the rotational movement, which might movement of the tip and reduce the amplitude of
increase the coronal transportation of debris (B€ urklein oscillation, affecting therefore the amount of stream-
et al. 2014). ing by constraining the file (Walmsley & Williams
In the present investigation, the final size of prepa- 1989).
ration was established based on the size of the previ- In the present study, the MM1500 prototype is
ous filling. The preparation was increased from size considerably smaller with size 15 at the tip and .02
25 (X2) to size 40 (F40 and R40). This increase taper compared to the Eddy with tip size 20 and .05
seems to represent a suitable balance between apical taper. That might confer to the prototype further
enlargement and preservation of tooth structure. space for oscillation and could compensate for its
Many studies advocate the enlargement of the apical lower driving frequency. Jiang et al. (2010) found no
diameter by two sizes (Hassanloo et al. 2007, difference in the effectiveness of the activation when
Roggendorf et al. 2010) beyond the initial prepara- comparing a size 15, taper .02 and a size 25, taper
tion size to reduce intracanal bacteria (Card et al. .04 tips of the EndoActivator but they were using the
2002) and to ensure better apical healing (Mickel same frequency for both tips.
et al. 2007, Rodrigues et al. 2017). Thus, improved The present findings corroborate the results of
treatment outcome of infected teeth with apical peri- others who found Sonic activation to be as efficient as
odontitis has been demonstrated after enlarging the ultrasonics in cleaning oval canals especially when
preparations (Saini et al. 2012). In addition, a directed towards recesses (Lumley et al. 1993). Neu-
prospective cohort study reported a high success rate haus et al. (2016) reported that SI at 6000 Hz seems
(89%) for the retreatment of mandibular molars to perform as well as or better than PUI, while Mar-
using contemporary techniques and preparation sizes tins et al. (2017) concluded that the additional sonic
of 35 to 40 with tapers of .04 to .06 (He et al. and ultrasonic cleaning methods were similar with
2017). respect to the removal of filling material. The conflict-
The second null hypothesis was rejected as the sup- ing results can possibly be explained by the differ-
plementary SI approach had improved the removal of ences in root canal morphology, the type of filling
residual filling material from distal canals of mandibu- material and/or retreatment procedures.
lar molars. The limitations of this study lie in its laboratory
The effectiveness of sonic activation is attributed to design. Furthermore, this study is only the second
acoustic streaming within the irrigant, generated by study to evaluate the 2Shape system in retreatment.
the oscillating tip. Such streaming fields produce More studies with different anatomical variations, pro-
hydrodynamic shear stress along the endosonic files tocols and other filling materials should be performed
and mainly at the tip (Ahmad et al. 1987, Walmsley to confirm the effectiveness of these instruments in
et al. 1989). Streaming depends upon the operating removing GP and sealer.
conditions such as power setting and constraints.
Even when the tip is constrained, streaming still
Conclusions
occurs along the entire length of the file (Lumley
et al. 1991). The Reciproc and 2Shape systems were both unable
There were no significant differences between the to completely remove GP and sealer from oval distal
Eddy system (polyamide tip) and the prototype canals of extracted mandibular molars. Supplemen-
MM1500 (P = 0.163). The sonic hand pieces run at tary irrigant activation using sonic devices signifi-
1500 Hz for MM1500 and 6000 Hz for Eddy. In cantly reduced the amount of filling remnants with
spite of this difference, the MM1500 was as effective no significant difference between MM1500 and Eddy
as Eddy in removing residual filling material. The systems.

8 International Endodontic Journal © 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd
 Kaloustian et al. Removal of filling material using different systems

from oval-shaped canals by using rotary, reciprocating,

Acknowledgements and adaptive motion systems. Journal of Endodontics 42,
The authors would like to thank Dr Nada Osta for her 793–7.
Da Rosa RA, Santini MF, Cavenago BC, Pereira JR, Duarte
help with the statistical analysis, Drs J!er^
ome Michetti
MA, So MV (2015) Micro-CT evaluation of root filling
and Chloe Noventa for their contribution to the data
removal after three stages of retreatment procedure. Brazil-
analysis.
ian Dental Journal 26, 612–8.
Dummer PM, Hutchings R, Hartles FR (1993) Comparison
Funding of two sonic handpieces during the preparation of simu-
lated root canals. International Endodontic Journal 26,
The work was supported by the Research Department 159–68.
of the Universit!e Saint-Joseph Beirut as part of a PhD Hassanloo A, Watson P, Finer Y, Friedman S (2007)
project (FMD 135)/there was no external funding. Retreatment efficacy of the Epiphany soft resin obturation
system. International Endodontic Journal 40, 633–43.
He J, White RK, White CA, Schweitzer JL, Woodmansey KF
Ethical approval (2017) Clinical and patient-centered outcomes of nonsur-
gical root canal retreatment in first molars using contem-
This article does not contain any studies with human
porary techniques. Journal of Endodontics 43, 231–7.
participants or animals performed by any of the
Helvacioglu-Yigit D, Yilmaz A, Kiziltas-Sendur G, Aslan OS,
authors. The use of human teeth was approved by Abbott PV (2014) Efficacy of reciprocating and rotary sys-
the institution’s ethical committee. tems for removing root filling material: a micro-computed
tomography study. Scanning 36, 576–81.
Jiang LM, Verhaagen B, Versluis M, van der Sluis LW
Informed consent
(2010) Evaluation of a sonic device designed to activate
All patients signed a formal consent allowing the irrigant in the root canal. Journal of Endodontics 36, 143–
extraction and use of the extracted teeth for experi- 6.
mental purpose as part as a routine procedure at the Jiang S, Zou T, Li D, Chang JW, Huang X, Zhang C (2016)
Effectiveness of sonic, ultrasonic, and photon-induced pho-
Faculty.
toacoustic streaming activation of NaOCl on filling mate-
rial removal following retreatment in oval canal anatomy.
Conflict of interest Photomedicine and Laser Surgery 34, 3–10.
Kaloustian MK, Nehme W, El Hachem C et al. (2019) Evalu-
The authors have stated explicitly that there are no ation of two shaping systems and two ultrasonic irrigation
conflicts of interest in connection with this article. devices in removing root canal filling material from mesial
roots of mandibular molars: a micro CT study. Dentistry
Journal 7, E2.
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10 International Endodontic Journal © 2019 International Endodontic Journal. Published by John Wiley & Sons Ltd