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Effectiveness of ProTaper, D-RaCe, and Mtworetreatment files with and without supplementaryinstruments in the removal of root canal fillingmaterial

B. Marques da Silva1, F. Baratto-Filho1, D. P. Leonardi1, A. Henrique Borges2, L. Volpato1 & F.Branco Barletta3

1Positivo University, Curitiba, Parana; 2University of Cuiaba, Mato Grosso; and 3Luterana University of Brazil, Canoas, Rio Grande

do Sul, Brazil

Abstract

Marques da Silva B, Baratto-Filho F, Leonardi DP,

Henrique Borges A, Volpato L, Branco Barletta F. Effec-

tiveness of ProTaper, D-RaCe, and Mtwo retreatment files with and

without supplementary instruments in the removal of root canal

filling material. International Endodontic Journal, 45, 927–932, 2012.

Aim To assess the efficacy of different retreatment

rotary files in removing gutta-percha and endodontic

sealer from canals.

Methodology Ninety straight single-rooted premo-

lars were prepared up to a size 30 and filled with gutta-

percha and sealer and then randomly assigned to six

retreatment groups (n = 15). Groups I, III, and V were

retreated using rotary systems ProTaper Universal

Retreatment (PTUR), D-RaCe, and Mtwo Retreatment,

respectively. Groups II, IV, and VI were retreated using

the additional instruments F4, size 40, .04 taper RaCe,

and size 40, .04 taper Mtwo, respectively. The roots

were split vertically, and images of the halves were

obtained using a high-resolution scanner and evalu-

ated with AutoCAD software to calculate the percent-

age of residual material. Data were analyzed with

Kruskal–Wallis and Student–Newman–Keuls tests

using a 5% significance cutoff (P < 0.05).

Results There were no statistically significant differ-

ences (P > 0.05) between groups when additional

instruments were used. The percentage of residual

material was lowest in the PTUR group and was

statistically significant only when compared to the

D-RaCe system (P = 0.0038).

Conclusions All root canals had residual filling

material after retreatment even when additional

instruments were used.

Keywords: gutta-percha removal, nickel–titanium,

root canal retreatment, rotary instruments.

Received 25 November 2011; accepted 13 March 2012

Introduction

Although root canal treatments have a high success

rate of more than 90% when properly conducted (Kim

& Kratchman 2006), failures may occur that are often

associated with poorly treated canals (Mollo et al.

2011). Problems related to canal anatomy (Torabine-

jad et al. 2009) and also microbial factors can explain

failure rates of around 8% for treated canals (Masiero &

Barletta 2005).

The primary goal of root canal retreatment is to treat the

infectious process through the removal of filling material,

debris, and microorganisms that cause apical periodontitis

(Saad et al. 2007, Zehnder & Paque 2011). Gutta-percha

and endodontic sealer are the most widely used filling

materials, and their effective removal in endodontic

retreatments is considered essential for success (Friedman

et al. 1993, Duncan & Chong 2011). Thus, root filling

materials should be retreatable (Grossman 1970).

Several retreatment techniques, such as the use

of nickel–titanium rotary instruments, have been

Correspondence: Flares Baratto-Filho, Rua Professor Pedro

Viriato Parigot de Souza, 5300 Campo Comprido, 81280-330

Curitiba/PR, Brazil (Tel: +55 41 3317 3406; fax +55 41

3317 3082; e-mail: [email protected]).

doi:10.1111/j.1365-2591.2012.02051.x

ª 2012 International Endodontic Journal International Endodontic Journal, 45, 927–932, 2012 927

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proposed (Baratto Filho et al. 2002, Bramante et al.

2010, Marfisi et al. 2010). These instruments are more

efficient than hand instrumentation; they reduce clin-

ical time and operator and patient fatigue (Somma et al.

2008). However, none of these techniques are totally

effective in removing filling material (Hammad et al.

2008, Pirani et al. 2009).

Several nickel–titanium rotary systems with different

features have been developed to improve efficiency and

retreatment success rates. Mtwo Retreatment and Pro-

Taper Universal Retreatment (PTUR) systems have been

evaluated previously (So et al. 2008, Bramante et al.

2010), whereas no comparative studies have analyzed

the recently developed D-RaCe System. Moreover, no

studies have compared the results obtained when these

instruments are used in combination with additional

instruments to improve removal of root canal filling.

Because the removal of filling material represents a

crucial step in retreatment success (Saad et al. 2007,

Hulsmann et al. 2011), the aim of this study is to

evaluate the efficacy of removing gutta-percha and

endodontic sealer from root canals using the PTUR,

Mtwo Retreatment, and D-RaCe System.

Material and methods

After ethics committee approval, 90 single-rooted

straight premolar teeth with fully formed apices and

no calcifications or internal resorption were used. To

standardize the cohort, the crowns were removed to

leave a 21-mm root.

A single operator prepared root canals in a step-down

sequence (Goerig et al. 1982). The cervical and middle

thirds were enlarged using Gates Glidden burs sizes 1, 2,

and 3 (Dentsply Maillefer, Ballaigues, Switzerland). The

apical third was prepared up to a size 30 K-type file

(Dentsply Maillefer), and the middle and cervical thirds

were flared and refined with size 55 K-type files

(Dentsply Maillefer) used to the length of the Gates

Glidden bur no 1 minus 1 mm. At each instrument

change, the root canal was irrigated with 2 mL of a 2.5%

NaOCl solution delivered using a syringe with a 27-

gauge needle (Ultradent, South Jordan, UT, USA). When

root canal instrumentation was completed, 17% ethy-

lenediaminetetraacetic acid (EDTA) was applied for

3 min (Masiero & Barletta 2005, So et al. 2008,

Takahashi et al. 2009, Bramante et al. 2010) for smear

layer removal followed by a final rinse with 5 mL of

distilled water to remove the previously used solutions to

allow better contact of the sealer with the root canal

walls. The root canals were dried using paper points and

filled with gutta-percha (Dentsply Maillefer) and cement-

based epoxy resin sealer (AHPlus, Dentsply DeTrey

GmbH, Konstanz, Germany) using thermomechanical

compaction with a hybrid technique (Tagger et al.

1984). This technique consists of the lateral compaction

of size 30 cold gutta-percha cones along with MF

accessory cones used with B finger spreaders (Dentsply

Maillefer) followed by the application of a size 40 gutta-

percha condenser (Dentsply Maillefer). After cutting-

back the fillings, root canals were sealed with Coltosol

(Coltene, Langenau, Germany) temporary filling, and

the teeth stored at 37 �C in 100% humidity for 2 weeks

(Pirani et al. 2009). After this period, the temporary

fillings were removed, and the teeth randomly assigned

to six groups according to the retreatment technique.

Group I: ProTaper Universal Retreatment group

(N = 15)

ProTaper Universal Retreatment (PTUR) instruments

were used to remove the filling material in a crown-down

technique as follows: D1 (size 30, .09 taper) for the

cervical third, D2 (size 25, .08 taper) for the middle third,

and D3 (size 20, .07 taper) for the apical third until the

working length was reached. The instruments were used

with an XSmart electric motor (Dentsply Maillefer) at a

speed of 300 rpm and with a torque of 2 N cm)1,

according to the manufacturer’s instructions.

Group II: ProTaper Universal Retreatment

Group + ProTaper F4 (N = 15)

The retreatment technique used in this group was the

same as that in group I, but the final instrumentation

was performed using ProTaper instrument F4.

Group III: D-RaCe Retreatment Group (N = 15)

D-RaCe retreatment instruments were used according

to the manufacturer’s instructions (speed and torque)

as follows: DR1 (size 30, .10 taper) at a speed of

1000 rpm and torque of 1.5 N cm)1 for the cervical

third and beginning of the middle third and DR2 (size

25, .04 taper) at 600-rpm speed and a torque of

0.7 N cm)1 at the working length.

Group IV: D-RaCe Retreatment Group + RaCe size

40, .04 taper (N = 15)

The retreatment technique used here was the same

as that in group III, but the final instrumentation

Rotary files in retreatment Marques da Silva et al.

International Endodontic Journal, 45, 927–932, 2012 ª 2012 International Endodontic Journal928

was performed using the sizer 40, .04 taper RaCe

instrument at a speed of 300 rpm and a torque of

1 N cm)1 according to the manufacturer’s instruc-

tions.

Group V: Mtwo Retreatment Group (N = 15)

In this group, the removal of filling material was

performed according to the manufacturer’s instructions

and using the Mtwo R2 (sizer 25, .05 taper) instrument

in all working lengths at a speed of 300 rpm and a

torque of 1.2 N cm)1.

Group VI: Mtwo Retreatment Group + Mtwo size

40, .04 taper

The removal of filling material was performed in the

same manner as that in group V, but the size 40, .04

taper Mtwo instrument was added as a supplemental

(file) at a speed of 300 rpm and a torque of 1.2 N cm)1

according to the manufacturer’s instructions. Table 1

shows system, instrument, size, taper, tip, and sequence

of the instruments of all groups.

During retreatment, root canals were irrigated with

2 mL of a 2.5% NaOCl solution at each instrument

change. When the retreatment was considered finished,

the root canals were irrigated with 3 mL of 17% EDTA

solution.

Retreatment was considered complete when no

gutta-percha or sealer was detected on the instrument

surfaces or inside the root canal or dentinal walls. A

dental operating microscope (Opto Dm 2003 General�Surgical Microscope, Miami, FL, USA) was used

throughout.

Each retreatment instrument was discarded after

being used in five root canals. All instruments were

used in a back-and-forth motion with gentle apical

pressure and with brushing movements against the

canal walls.

Evaluation of residual material

To evaluate the residual filling material, the teeth were

grooved buccolingually using a double-sided diamond

disc and sectioned longitudinally using an Ochsenbein

chisel. Both root halves were scanned using a high-

resolution scanner (HP 4490; Hewlett Packard, Palo

Alto, CA, USA) at 1200 dpi. The images were trans-

ferred to image analysis software (Autocad 2004;

Microsoft, Redmond, Washington, USA) to measure

the areas of residual filling material and root canal

walls.

The area of residual filling on all root canal surfaces

(total area) and in each root canal third (cervical,

middle, and apical) was measured. The percentage of

residual filling material in the root canal walls (A) was

calculated using the following equation: A = (area of

the remnant · 100)/area of the root canal.

Statistical analysis for the area of residual filling

material was performed using the Kruskal–Wallis test

and Student–Newman–Keuls test with a significance

level of <0.05.

Results

All teeth had filling material remnants in the canal,

except for two teeth in group II, two teeth in group IV,

and one tooth in group VI. Table 2 shows the averages

of the area of residual filling material to the area of root

canals after instrumentation for each group.

Analysis of the total area revealed the least remain-

ing material in groups I, II, IV, and VI. The amount of

material was significantly different when compared to

groups III and V. In the groups with additional

instrumentation, no statistical differences were found.

All groups had similar results in the cervical third. In

the middle third, the comparison between groups

without additional instrumentation revealed that

removal of filling material was more effective in group

Table 1 System, instrument, size, taper,

tip, and sequence of the instrumentsSystem Instrument Size Taper Tip Sequence

Protaper D1 30 .09 Cutting tip GI: D1, D2, D3

D2 25 .08 Noncutting tip GII:D1, D2, D3, F4

D3 20 .07 Noncutting tip

F4 40 .06* Noncutting tip

D-RaCe DR1 30 .10 Cutting tip GIII: DR1, DR2

DR2 25 .04 Noncutting tip GIV: DR1, DR2,

40, .04

40, .04 40 .04 Noncutting tip

M-Two R2 25 .05 Cutting tip GV: R2

40, .04 40 .04 Noncutting tip GVI: R2, 40, .04

* in the first 3 mm.

Marques da Silva et al. Rotary files in retreatment


I than in groups III (P = 0.0005) and V (P = 0.0036).

However, with the use of additional instrumentation,

groups II, IV, and VI had similar results. The use of an

additional instrument resulted in a statistically signif-

icant improvement between group III and group IV

(P = 0.0313).

In the apical third, all groups without additional

instrumentation had similar results. However, the use

of an additional instrument improved the results of

group IV when compared with group VI (P = 0.0294).

There was an increase in effectiveness only when group

IV was compared with group III (P = 0.0017).

Discussion

A major goal of root canal retreatment is removal of

filling material. This allows effective action of instru-

ments and irrigating solutions on debris and microor-

ganisms responsible for apical periodontitis (de Oliveira

et al. 2006, Somma et al. 2008, Tasdemir et al. 2008,

Pirani et al. 2009, Ring et al. 2009, Takahashi et al.

2009). However, complete removal of filling material is

challenging (Ferreira et al. 2001, Giuliani et al. 2008,

Marfisi et al. 2010).

The results of the present study are in accordance

with the literature; residual filling material was found

in 95% of the samples. Complete removal was achieved

in five teeth, but this was not statistically significant.

The complete removal in some samples is consistent

with other reports (Baratto Filho et al. 2002, Pirani

et al. 2009).

Most studies in the literature standardize the length

of the teeth through the section of the crowns

(Tasdemir et al. 2008, Zanettini et al. 2008, Takahashi

et al. 2009). In the current study, standardization was

achieved by partial removal of crowns to attain the

same working length in all samples. Complete removal

of the crowns was not performed because it would be a

less accurate simulation of daily practice.

This study used vertical splitting to obtain images for

observation after retreatment. Vertical splitting is a

well-established method (Baratto Filho et al. 2002,

Takahashi et al. 2009). To obtain images of the root

halves, a high-resolution scanner (1200 dpi) was used.

This method offers advantages over other techniques

because it is easy to use and the distance between

object and device is constant, thus enabling image

standardization.

Several techniques for the removal of filling material

have been described (Peters et al. 2002, Masiero &

Barletta 2005, Pirani et al. 2009). Some dentists use

nickel–titanium rotary files for this purpose as these

systems reduce the clinical time and operator and

patient fatigue (Tasdemir et al. 2008).

In this study, three recently developed retreatment

nickel–titanium rotary systems were used, in addition

to using supplementary instruments to complement the

removal of filling material. The variables between the

designs and tapers of the retreatment systems studied

have not affected the performance of the systems

because different clinical situations are routine to these

systems. In addition, the standardization of additional

instrumentation was made and performed using a size

40 apical diameter, .04 taper (Mtwo and Race) or .06

(PTU) instruments and according to the literature

(Baratto Filho et al. 2002, Hammad et al. 2008). The

additional instrumentation aimed to refine the root

canal preparation, especially in the apical third, as the

diameter of the apical retreatment instrument is

normally in a clinical situation smaller than that of

the file used for the instrumentation. Thus far, no

studies have compared the effectiveness of these

systems for retreatment with or without the use of

additional instrumentation.

Few studies have compared the results of the PTUR

and Mtwo Retreatment systems (Somma et al. 2008,

Bramante et al. 2010). Moreover, no studies have

evaluated the results of D-RaCe retreatment rotary files.

Therefore, this study aimed to compare the retreatment

ability of these systems.

Presence of residual filling material was expected in

groups I, III, and V because retreatment instruments

with a diameter smaller than that of the apical root

canal area were used in these groups. Analysis of the

total area of residual filling material showed that PTUR

was more efficient. However, this difference was only

Table 2 Mean and standard deviation of

the area of residual filling material by

canal region after instrumentation. For

each column, values followed by same

letters are statistically similar (P > 0.05)

Cervical Middle Apical Total

Group I 0.016 ± 0.033a 0.051 ± 0.070c 0.263 ± 0.132a 0.064 ± 0.035bc

Group II 0.037 ± 0.050a 0.064 ± 0.069c 0.138 ± 0.107bc 0.063 ± 0.053c

Group III 0.067 ± 0.082a 0.235 ± 0.125a 0.271 ± 0.112a 0.158 ± 0.086a

Group IV 0.016 ± 0.024a 0.127 ± 0.147bc 0.113 ± 0.121c 0.070 ± 0.066bc

Group V 0.053 ± 0.088a 0.207 ± 0.140ab 0.189 ± 0.130abc 0.124 ± 0.091ab

Group VI 0.031 ± 0.040a 0.128 ± 0.112abc 0.254 ± 0.201ab 0.095 ± 0.067abc



significant when compared to the D-RaCe system.

These results may be related to the convex triangular

cross-section of the PTUR instruments that renders its

internal mass larger than the internal mass of the

Mtwo Retreatment and D-RaCe instruments (Giuliani

et al. 2008, Bramante et al. 2010). This feature

promotes the heating of gutta-percha and may facili-

tate its removal (Bramante et al. 2010). In addition, the

root canal area prepared by the PTUR instruments is

larger owing to their greater taper. The D-RaCe system

was less effective when used without the additional

instrumentation. This result may be related to the

instrument DR2 (size 25, .04 taper); this instrument is

thinner and has an inactive tip, making it difficult to

penetrate the gutta-percha.

ProTaper Universal Retreatment removed more

material in the cervical third of groups I, III, and V.

This effect may be related to the larger area of the root

canal after instrumentation in group I. However, this

difference was not statistically significant and is in

accordance with those of other studies (Duarte et al.

2010). In the cervical third, it is easier to view the

filling material, especially using clinical microscope;

this would facilitate its removal by instruments because

the instruments are used in a brushing motion against

the root canal walls. In the middle third, group I had

the least amount of residual filling material. This result

is probably due to the larger area for the PTUR than

that for the other systems. In the apical third, group V

had less material, likely because the Mtwo Retreatment

instrument has a greater apical diameter and active tip,

facilitating removal of filling material.

Amongst groups with additional instrumentation,

groups II, IV, and VI showed similar results regarding

the total area of residual filling material. When the

three regions of the teeth were assessed, the cervical

and middle thirds were similar. However, in the apical

third, there was a statistically significant difference

between groups IV and VI. Despite having similar

diameters, the RaCe system file removed more material

than those of the ProTaper F4 instrument and Mtwo.

The performance of RaCe size 40, .04 taper is in

accordance with the findings of other studies that have

evaluated its shaping ability (Schafer & Vlassis 2004,

Schirrmeister et al. 2006), and this may be related to its

design. These instruments have a simple triangular

cross-section that is associated with a high cutting

ability. Moreover, they have alternating cutting edges

that prevent the screw effect, favoring penetration into

the filling material. The flute area of these instruments

allows coronal extrusion of filling material.

This study also observed that additional instrumen-

tation improves the removal of filling material. As

expected, all groups showed improvement with the use

of additional instrumentation. However, the improve-

ment was significant between groups III and IV owing

to leaving more material when using the D2 D-Race

instrument, as explained earlier. Group III had the most

material compared with those of all other groups.

However, use of additional instrumentation did not

result in significant improvement in the removal of

filling material. In addition, when the tooth thirds were

considered separately, there was a significant improve-

ment in the apical portion, except in groups V and VI

where Mtwo was used. Although the difference was not

statistically significant, it was not expected to have

more filling material in apical third after using the

additional instrument. This unexpected result could be

explained by variations in canal anatomy and the

universal inability of all instruments to contact 100%

of the root canal wall. In group VI, an Mtwo size 40,

.04 taper additional instrument was used. This has an

S-shaped cross-section, an increasing pitch length in

the apical–coronal direction, a noncutting tip, and a

positive rake angle with two cutting edges (Schafer

et al. 2006). This design feature may allow them to

reach the apical third whilst bypassing filling material

(Tasdemir et al. 2008).

Conclusions

None of the systems completely removed filling material

from the root canal. Amongst groups in which addi-

tional instrumentation was used, the PTUR was the

most effective system, especially when compared with

D-RaCe. There were no differences in outcomes

between groups with the use of additional instrumen-

tation.

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