Basic Research—Technology

Efficacy of Reciprocating Instruments for Removing FillingMaterial in Curved Canals Obturated with a Single-coneTechnique: A Micro–computed Tomographic AnalysisLincoln de Campos Fruchi, DDS,* Ronald Ordinola-Zapata, DDS, MSc, PhD,†

Bruno Cavalini Cavenago, DDS,† Marco Antonio Hungaro Duarte, DDS, MSc, PhD,†

Carlos Eduardo da Silveira Bueno, DDS, MSc, PhD,*and Alexandre Sigrist De Martin, DDS, MSc, PhD*

Abstract

Introduction: The aim of this study was to evaluate theefficacy of nickel-titanium reciprocating instrumenttechniques and passive ultrasonic irrigation (PUI) for re-treatment in curved canals and obturated with corre-spondent single cones. Methods: Twenty molars wereselected with mesial-buccal canals with curvatures be-tween 20� and 40�, and they were instrumented witha Reciproc R25 instrument (VDW, Munich, Germany)in a reciprocating motion and obturated with singlecones and AH Plus sealer (Dentsply Maillefer, Bal-laigues, Switzerland). The teeth were divided into 2groups (n = 10) according to the instrument used forthe removal of filling material: group 1: Reciproc R25 in-strument and group 2: WaveOne Primary instrument(Dentsply Maillefer). The analysis of the remnant fillingmaterial was made through micro–computed tomo-graphic imaging after the use of reciprocating instru-ments and again after the use of PUI with xylene. Theeffective time of retreatment was registered. Results:The filling material of the root canal was efficientlyremoved (P < .05) for both groups. The percentage ofremoval of filling materials was 93% for the Reciprocgroup and 92% for the WaveOne group. There wereno statistical significant differences (P > .05) betweenthe groups in relation to the removal of filling materialability and the time needed for the procedure. The effec-tive time for the removal of filling material was 78.7 sec-onds and 89.5 seconds for the Reciproc and WaveOnegroups, respectively. Conclusions: It was concludedthat both instruments efficiently but not completelyremoved the filling material from inside the root canals.The use of xylene with PUI increased the removal offilling material a little, but it was not statically signifi-cant. (J Endod 2014;40:1000–1004)

From the *Postgraduate Program in Endodontics, S~ao LeopoldoBauru Dental School, University of S~ao Paulo, Bauru, S~ao Paulo, Bra

Address requests for reprints to Dr Lincoln de Campos Fruchi,lincolnfruchi@uol.com.br0099-2399/$ - see front matter

Copyright ª 2014 American Association of Endodontists.http://dx.doi.org/10.1016/j.joen.2013.12.011

1000 Fruchi et al.

Key WordsMicro–computed tomography, reciprocating motion, root canal retreatment

Endodontic retreatments are a challenge with a high level of difficulty, and they aretime-consuming (1). It has been considered that the use of rotary instruments

could reduce the fatigue and time of endodontic retreatments (2). Furthermore,the use of balanced forces, such as those proposed by Roane et al in 1985 (3),allows one to maintain the original canal shape in curved root canals. Yared (4)introduced the reciprocating motion with new nickel-titanium (NiTi) instrumentsbased on this concept of balanced forces, and it was shown to be effective in thepreparation of the root canal using 1 instrument. Reciprocating motion is similarto the balanced forces because their counterclockwise angle was greater than theclockwise movement and led the file to continuously move toward the apex (5).Furthermore, the M-wire alloy increases the resistance and flexibility of the recipro-cating instruments (6). This same technique is also used to remove filling materialfrom the root canals in a brushing motion. In the literature, just 1 study analyzedthese new NiTi reciprocating instruments in root canal retreatment on teeth withstraight roots (7). There are few studies about the efficacy of filling material removalwith NiTi rotary instruments in curved canals, mainly for resin sealers, which are themost used sealers nowadays, and for the removal of filling material in curved canalswith reciprocating instruments (2, 8, 9).

Other studies used an invasive and destructive methodology to analyze the remnantfilling material, and they were analyzed through 2-dimensional images (2, 5, 7). Micro–computed tomographic (micro-CT) imaging offers a noninvasive and reproducibletechnique for 3-dimensional (3D) evaluation of debris left inside root canals (10).The aim of this study was to compare, through micro-CT imaging, the remaining fillingmaterial after instrumentation using reciprocating files and again after passive ultra-sonic irrigation (PUI) with xylene.

Materials and MethodsAfter ethics committee approval (protocol 2012/0122), 45 human upper mo-

lars from a total of 80 molars with curved mesial-buccal canals donated by S~ao Leo-poldo Mandic School of Dentistry, Campinas, S~ao Paulo, Brazil, were selected. Thecrowns were flattened to a 16-mm length with a diamond disc (FKG, Dentaire,

Mandic Dental Research Center, Campinas, S~ao Paulo, Brazil; and †Department of Endodontics,zil.rua Frei Caneca, 1212, cj 84, Cerqueira C�esar, S~ao Paulo, SP, Brazil 01307-002. E-mail address:

JOE — Volume 40, Number 7, July 2014

TABLE 1. Median, Minimum, and Maximum Values of the Volume (mm3) of the Initial Filling Material (IM) after the Removal of Filling Material (R) and after PUI ofthe Studied Groups in the Different Levels and Total Length of the Root Canal

Reciproc WaveOne

IM R PUI IM R PUI

Apical 0.422a (0.086–0.741) 0.015b (0–0.402) 0.008b (0–0.321) 0.445a (0.251–0.685) 0.015b (0.001–0.292) 0.015b (0.001–0.153)Middle 1.095a (0.624–1.501) 0.048b (0–0.275) 0.029b (0–0.195) 1.039a (0.872–1.666) 0.081b (0.000–0.159) 0.081b (0.000–0.156)Cervical 1.520a (1.024–2.381) 0.094b (0.003–0.232) 0.084b (0.003–0.219) 1.605a (1.034–1.985) 0.140b (0.000–0.338) 0.074b (0.000–0.304)Total 3.162a (1.775–4.623) 0.244b (0.045–0.787) 0.207b (0.048–0.590) 3.073a (2.685–3.738) 0.243b (0.016–0.631) 0.203b (0.016–0.452)

PUI, passive ultrasonic irrigation.

Different letters indicate the statistically significance differences (P < .05) between each intragroup procedure.

Basic Research—Technology

Switzerland) initially established with a digital caliper. Next, they hadthe patency confirmed with a #15 K-file (Dentsply Maillefer, Bal-laigues, Switzerland) under 8� magnification with an operative mi-croscope (Alliance, S~ao Paulo, Brazil). The real length of the teethwas observed by the tip of the file in the apex, and the workinglength was established 1 mm shorter. They were instrumented withR25 Reciproc files (VDW, Munich, Germany) in the respective Recip-roc program of the VDW Silver Reciproc electric motor. The file wasintroduced until resistance was felt and used with 3 in-and-out peck-ing motions with light apical pressure. After that, the instrument wasremoved and cleaned. The canals were instrumented with 2.5% so-dium hypochlorite and irrigated with 2 mL of this same solution eachtime after the 3 pecking motions until reaching the working length.The final irrigation was performed with 1 mL 17% EDTA for 1 minuteand a final rinse with 2 mL 2.5% sodium hypochlorite with a 30-GNaviTip needle (Ultradent Products Inc, South Jordan, UT) (11).Next, they were dried with R25 paper points and obturated withR25 single cones (VDW) and AH Plus sealer (Dentsply Maillefer).The sealer was put in the cone tip and inserted into the canal ina single movement, and then the exceeded part of the cone in thecoronal section was cut with a Touch’n Heat instrument (Sybro-nEndo, Orange, CA). The crowns were sealed with Citodur (Dorident,Wien, Austria) temporary restorative material and stored at 37�C and100% humidity for 3 months.

The teeth were digitally radiographed with sensor number 1 ofthe Schick CDR X-ray digital system (Schick Technologies, Long Is-land, NY) with 0.16 seconds of exposition time in the buccolingualand mesial-distal directions. The digital radiographs were evaluatedregarding the quality of obturation, and 20 teeth with curvature an-gles between 23.2� and 39.89� were evaluated according to theSchneider method (12). The teeth were selected and divided into2 groups with similar characteristics to ensure the homogeneity be-tween the groups. In the WaveOne group (n = 10), the filing ma-terial was removed with the Primary WaveOne files (DentsplyMaillefer), and in the Reciproc group (n = 10), the filling materialwas removed with the R25 Reciproc files. An electric motor VDWSilver Reciproc with the respective programs for each file, Reciprocor WaveOne, was used with the same protocol of the initial instru-

TABLE 2. Median, Minimum, and Maximum Values of the Volume in Percentage (Different Levels and Total Length of the Root Canal

Reciproc

R PUI

Apical 97b (44–100) 98b (55–10Middle 96b (77–100) 97b (84–10Cervical 94b (78–100) 94b (82–10Total 93b (77–98) 93b (83–98

PUI, passive ultrasonic irrigation.

The same superscript letters in each row indicate no statistically significant differences (P > .05).

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mentation and irrigation. After reaching the working length, a brush-ing motion of the instrument was used until the complete removal ofthe filling material. The complete removal of the filling material wasdetermined through the appearance of smooth walls and when theremaining filling material was not observed on the file and the pres-ence of gutta-percha was not visible on the canal walls with a clinicalmicroscope under 8� magnification (13). The same protocol of theirrigation with 2 mL 2.5% sodium hypochlorite each time after 3pecking motions until reaching the working length was performed.One drop (0.8 mL) of xylene solvent was put in the pulp chamberfor 1 minute before starting the first penetration of the instrumentwith the objective to facilitate the penetration into the canal to themedium third. The xylene solvent was not used in the latter stepsof the instrumentation. Both in the initial instrumentation and inthe filling material removal, just 1 file was used for each canaland then discarded. The effective time of desobturation was re-corded. The effective time is only the time of action of the instrumentinside the canal.

The teeth were mounted on a custom attachment and scanned in amicro-CT system (SkyScan 1174; Bruker-microCT, Kontich, Belgium).The 50-kv, 800-mA, and 30-mm voxel parameters were used beforeand after desobturation with the same protocols. Another scan wasmade after PUI with 1 drop (0.8 mL) of xylene solvent with an Irrisonictip (Helse, S~ao Paulo, SP, Brazil) driven by an ultrasonic device (JetSonic; Gnatus, SP, Brazil) with 20% of the power scale according tothe manufacturer’s instructions. It was applied for 20 seconds, 1 mmfrom the working length, and repeated 3 times. A final irrigation wasmade with 2 mL 2.5% sodium hypochlorite with a 30-G NaviTip needle.The samples were reconstructed with NRecon software version 1.6.3(Bruker-microCT, Kontich, Belgium), and the axial cross-sectionswere obtained. Volumetric analyses of the 3D models were made withsimilar parameters with CTAn v.1.12 software (Bruker-microCT). Themean length of the canals measured through micro-CT imaging was9.81 mm. Three segments of 3 mm, which we named the apical, middle,and cervical, were studied. The filling material volume was calculatedfrom the binarized area inside the region of interest with the same param-eters. The volumes were recorded and converted into percentages rela-tive to the initial volume of the filling material.

%) of the Filling Material Removal and after PUI in the Studied Groups in the

WaveOne

R PUI

0) 97b (53–100) 97b (58–100)0) 92b (84–100) 92b (89–100)0) 91b (82–100) 95b (84–100)) 92b (83–99) 93b (89–99)

Reciprocating Instruments for Removing Filling Material 1001

Figure 1. Micro-CT reconstructions of representative samples of the (A–C) Reciproc and (D–F) WaveOne groups. The figure shows (A and D) filling material,(B and E) post filling material removal, and (C and F) post PUI with xylene.

Basic Research—Technology

The normality of the data was analyzed by the Shapiro-Wilk test,and because of the absence of normality, the Mann-Whitney test wasused to compare the groups regarding the total and effective time offilling material removal and the relation of the percentage reductionof filling material. The Wilcoxon test was used to compare the percent-age reduction of the filling material for intragroup comparison. TheFriedman and Dunn tests were used to compare the reduction of thevolume of each filling material removal procedure. The significancelevel was established at 5%.

ResultsThe instruments evaluated in this study efficiently (P < .05), but

not completely, removed the filling material from inside the root canalsfor all levels of the root canal length (Tables 1 and 2, Fig. 1). Themedianvalue of the percentage of filling material removal was 93% for the Re-

TABLE 3. Median, Minimum, and Maximum Values of the Curvature Angle ofthe Root canal; the Effective of the Filling Material Removal (seconds); andMean, Minimum, and Maximum Canal Lengths (mm) of the Studied Groups

Reciproc WaveOne

Angle 29.5a (23.2–38.5) 30.5a (23.2–39.8)ET 78.7a (72–180.7) 89.5a (68–120.1)CL 9.70a (9.018–10.767) 9.92a (9.013–11.58)

CL, canal length; ET, effective time of the filling material removal.

The same superscript letters in each row indicate no statistically significant differences (P > .05).

1002 Fruchi et al.

ciproc group and 92% for the WaveOne group (Table 2). The medianeffective times for the procedures were 78.7 seconds for the Reciprocgroup and 89.5 seconds for the WaveOne group (Table 3). No staticallysignificant differences (P > .05) between groups were observed.

DiscussionThe efficacy of filling material removal is important for disinfec-

tion and to reduce the bacteria left inside the canal. The effectivenessof cleaning and shaping of the reciprocating instruments was foundto be similar to the Self-Adjusting File (SAF) (ReDent-Nova, Ra’anana,Israel) and Twisted File (SybronEndo) in the preparation of mesialcanals of mandibular molars (14). Another study evaluated changesof the basic geometric parameters of oval-shaped canals (ie, area,perimeter, roundness, and diameter) after instrumentation withWaveOne, Reciproc, ProTaper (Dentsply Maillefer), and SAF andconcluded that when used in a brushing motion, all instruments per-formed similarly until they touched the dentin walls (15). Recipro-cating motion was shown to leave more debris, so specialimportance should be applied to irrigation when reciprocating in-struments are used (16). However, in another study, Reciproc wasshown to produce less debris than ProTaper and SAF but with nostatistically significant differences (17). Regarding the maintenanceof the original canal shape, both the rotary and reciprocating systemswere shown to be safe. A study that compared the WaveOne andTwisted File systems found an increased canal transportation of

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Basic Research—Technology

WaveOne compared with Twisted File, but both systems showed satis-factory preservation of the original canal shape (18).

In the present study, xylene was chosen as a solvent to facilitate theability to remove the gutta-percha, and it is a substance with a moreeffective dissolving action (19). Solvents lead to more filling materialremnants on the root canal walls and inside the dentinal tubules.Thus, its use should be considered just in cases of difficulty in reachingthe working length, which is the situation found in curved canals (20).This study also evaluated filling material removal with xylene activatedthrough PUI. The use of ultrasound in irrigation improved the removalof soft and necrotic tissues, debris, smear layers, and bacteria (21). Af-ter removal of the greater part of the filling material, the solvents can beused to enhance the canal cleaning (22). PUI with xylene slightlyincreased filling material removal for both groups at all levels butwithout any statistically significant difference. This finding could becaused by the fact that in curved canals, ultrasound irrigation has alower efficacy than in straight canals (23). These results may also becaused by the fact that the Irrisonic tip is a passive file for ultrasonicirrigation, which may have little influence in removing remnants offilling materials from the root canals. Further studies should be con-ducted on the possible use of an active ultrasonic file to enhance clean-ing in these cases and investigate the possibility of the use of these files incurved canals.

The single-cone and lateral compaction techniques did notdiffer radiographically and are faster and easier to operate (24).In 1 study, it was shown that a constant tapered single cone didnot differ regarding the percentage of filling areas compared withthe lateral compaction technique (25). The technical quality ofroot fillings on radiographs and periapical health are associated(26). However, several studies about leakage showed that the qualityof obturation with warm gutta-percha was better than that of thetapered single-cone technique (27, 28). Furthermore, the use ofsingle cones should be restricted to straight and rounded canals asused in this study because in irregular or elliptic canals it maylead to the formation of voids (29).

Micro-CT analysis was chosen because it is an excellent, noninva-sive, and nondestructive method for quantitatively and qualitatively eval-uating root canals (30). Micro-CT imaging is ideal to quantify the volumeof debris and filling material before and after instrumentation (10).

It was observed that in the canals with curvatures between 23.2�and 39.8�, the 2 reciprocating systems favored a faster removal of thefilling material than other studies that evaluated the use of the ProTapersystem to remove the filling material of straight canals obturated withgutta-percha and AH Plus (7, 31, 32). Furthermore, the reciprocatingtechniques seem to be faster than most techniques regardinginstrumentation time (5, 33). Mtwo (VDW, Munich, Germany) andReciproc have an identical S-shaped cross-section with sharp cuttingedges, whereas ProTaper and WaveOne have a triangular or modifiedtriangular cross-section, resulting in a smaller cutting efficiency (5).The increased cutting ability of Reciproc could produce a better efficacyto remove the filling material (15). The findings of our study showed nostatistical difference between the 2 systems, even if Reciproc registered afaster effective time than WaveOne in the removal of the filling materialused.

Under the experimental condition, filling material removal wasefficient for all segments (apical, middle, and cervical) in the 2 groups.Considering the total length of the canal evaluated, filling materialremoval was very efficient (Table 2), and the median values of the per-centage of filling material removal was 93% for the Reciproc group and92% for the WaveOne group.

In conclusion, both instruments efficiently, but not completely,removed the filling material from inside the root canals. The use of

JOE — Volume 40, Number 7, July 2014

the xylene solvent with passive ultrasonic agitation did not statisticallyimprove the removal of the obturation material.

AcknowledgmentsThe authors deny any conflicts of interest related to this study.

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