Comparison of the Efficacy of Three Chelating Agents inSmear Layer RemovalSedigheh Khedmat, DDS, MSc, and Noushin Shokouhinejad, DDS, MSc

Abstract

The purpose of this study was to compare the efficacyof SmearClear (Sybron Endo, Orange, CA), 17% EDTA,and 10% citric acid in smear layer removal. Forty-eightextracted single-rooted human teeth were randomlydivided into 4 groups (n � 12) and instrumented usingMtwo nickel-titanium rotary instruments. Each canalwas subsequently irrigated with one of the followingsolutions: 5.25% NaOCl (control), SmearClear, 17%EDTA, or 10% citric acid. After that, all the specimenswere subjected to irrigation with 5.25% NaOCl. Theteeth were then processed for scanning electron mi-croscopy (SEM), and the removal of the smear layer wasexamined in the coronal, middle, and apical thirds. Theresults showed that there were no significant differ-ences in the efficacy of three chelating agents at alllevels of the root canals. The comparison of three onethirds in each group showed no significant difference inthe SmearClear and EDTA groups. However, the effi-cacy of citric acid was significantly less in the apicalthird compared with the coronal and middle thirds ofthe canals. In conclusion, the protocol used in thisstudy was not efficient to completely remove thesmear layer especially in the apical third of the canal.(J Endod 2008;34:599–602)

Key Words

Chelating agents, citric acid, EDTA, smear layer,SmearClear

Studies have shown that mechanical instrumentation of the root canals leaves a smearlayer covering the dentinal walls (1, 2). This layer contains inorganic and organicmaterials (1). Despite the controversy over keeping or maintaining the smear layer, ithas been demonstrated that the smear layer itself may be infected and may protect thebacteria within the dentinal tubules (3). The smear layer has also been shown to hinderthe penetration of intracanal disinfectants (4) and sealers (5) into dentinal tubules andhas the potential of compromising the seal of the root canal filling (6, 7).

For effective removal of both organic and inorganic components of the smearlayer, combined application of NaOCl and a chelating agent, such as EDTA, is recom-mended (8–10). It has been reported that the smear layer was completely removed by17% EDTA for 1 minute followed by 5% NaOCl (11). On the other hand, the applicationof EDTA for more than 1 minute (10–13) and in volume more than 1 mL (10, 12, 13)has been reported to be associated with dentinal erosion. Crumpton et al. (14) showedthat the smear layer was efficiently removed using 1 mL of 17% EDTA for 1 minutefollowed by 3 mL of 5.25% NaOCl as final irrigants.

Citric acid may also be used for the smear layer removal. Concentrations rangingfrom 1% to 50% have been investigated (15–20). Wayman et al. (17) showed that theuse of 10% citric acid and 2.5% NaOCl is a very effective approach for the smear layerremoval. Di Lenarda et al. (21) reported no or a negligible difference in smear layerremoval obtained by citric acid and EDTA.

SmearClear (Sybron Endo, Orange, CA) is a product recently introduced for re-moving the smear layer. It is a 17% EDTA solution including a cationic (cetrimide) andan anionic surfactant. The only published study to date comparing SmearClear withEDTA in removing the smear layer in the apical and middle thirds of the root canalshowed that the surfactants within the SmearClear did not improve its efficiency (22).

This study aimed to compare the efficacy of SmearClear, 17%EDTA, and 10% citricacid in combination with 5.25% sodium hypochlorite as final irrigants in the removal ofthe smear layer in the coronal, middle, and apical thirds of the instrumented root canal.

Materials and MethodsForty-eight freshly extracted human teeth with straight single root canals stored in

0.1% thymol were selected for this study. The teeth were decoronated to standardizedroot length of 12 mm and randomly divided into 4 groups (n � 12). The workinglengths were measured by deducting 1 mm from lengths recorded when tips of #10 or#15 K-files (Dentsply Maillefer, Tulsa, OK) were visible at the apical foramina. Thespecimens were prepared using Mtwo Ni-Ti rotary instruments (VDW, Munich, Ger-many). Five instruments were used at the working length in each canal according to themanufacturer’s instructions in the following sequence: (1) size 10, .04 taper; (2) size15, .05 taper; (3) size 20, .06 taper; (4) size 25, .06 taper; and (5) size 30, .05 taper.

Each instrument was only used for the preparation of five teeth. After using each fileand before proceeding to the next, canals were irrigated with 2 mL of 5.25% NaOCl(Vista Dental Products, Racine, WI). After instrumentation, all teeth underwent finalirrigation as follows: (1) control group, 1mL of 5.25% NaOCl for 1 minute followed by3mL of 5.25% NaOCl; (2) SmearClear group, 1mL of SmearClear for 1minute followedby 3 mL of 5.25% NaOCl; (3) EDTA group, 1 mL of 17% EDTA (Pulpdent, Watertown,MA) for 1 minute followed by 3 mL of 5.25% NaOCl; and (4) citric acid group, 1 mL of10% citric acid (Merck KGaA, Darmstadt, Germany) for 1 minute followed by 3 mL of5.25% NaOCl.

From the Department of Endodontics, School of Dentistry/Dental Research Center, Medical Sciences/University of Teh-ran, Tehran, Iran.

Supported by Tehran University of Medical Sciences &Health Services, Tehran, Iran (grant no 132/8543).

Address requests for reprints to Dr Noushin Shokouhine-jad, Department of Endodontics, Faculty of Dentistry, TehranUniversity of Medical Sciences, Ghods Ave, Enghelab St, Te-hran, Iran. E-mail address: shokouhinejad@yahoo.com.0099-2399/$0 - see front matter

Copyright © 2008 by the American Association ofEndodontists.doi:10.1016/j.joen.2008.02.023

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The solutions were introduced into the canals by means of a 30-Gneedle, which penetrated to within 1 to 2 mm from the working length.Then, the root canals were irrigated with 5 mL of distilled water anddried with paper points.

Finally, two longitudinal grooves were prepared on the buccal andlingual surfaces of each root using a diamond disc without penetrationinto the canal. The roots were then split into two halves with a chisel. Foreach root, the half containing the most visible part of the apex wasconserved and coded. The coded specimens were then mounted onmetallic stubs, gold sputtered, and examined by a scanning electronmicroscope (DSM 940 A; Carl Zeiss, Oberkochen, Germany). After gen-eral survey of the canal wall, 12 scanning electronmicroscopy photomi-crographs were taken at magnifications of 1,000� and 2,000� at thecoronal (10 mm to apex), middle (6 mm to apex), and apical (2 mm toapex) thirds of each specimen. Some areas were also observed at ahigher magnification (5,000�).

The amount of smear layer remained on the surface of the rootcanal or in the dentinal tubules was scored according to the followingcriteria (10): 1� no smear layer: no smear layer was detected on thesurface of the root canals and all tubules were clean and open; 2 �

moderate smear layer: no smear layer was observed on the surface ofthe root canal, but tubules contained debris; and 3� heavy smear layer:the smear layer covered the root canal surface and the tubules.

Approximately 600 scanning electron microscopy photomicro-graphs were scored by an endodontist who was unaware of the codingsystem to exclude observer bias. Evaluation was repeated twice for thefirst 20 specimens to ensure intraexaminer consistency.

Data were analyzed using Kruskal-Wallis and Mann-WhitneyU tests; p values were computed and compared with the p � 0.05level.

ResultsTwo specimens in control group were excluded from the study

because the canals were perforated by disc during preparation for SEMevaluation. The results for smear layer scores in each group are pre-sented in Table 1.

The examination of the surface of root canal walls in control groupshowed the presence of a heavy smear layer throughout the entire lengthof the root canals (Fig. 1A). Most samples of SmearClear group showed

TABLE 1. Mean Smear Scores ( SD) and Statistical Comparison of the Remaining Smear Layer among the Coronal, Middle, and Apical Thirds of the Canals inEach Group

Group

Coronalthirdscores Mean

Middle thirdscores Mean

Apical thirdscores Mean

pvalue

1 2 3 1 2 3 1 2 3

Control (n � 10) 0 0 10 3.00 0 0 10 3.00 0 0 10 3.00 1

SmearClear (n � 12) 4 8 0 1.6 0.4 4 8 0 1.6 0.4 3 6 3 2 0.7 0.3

17% EDTA (n � 12) 8 4 0 1.3 0.4 8 3 1 1.4 0.6 5 7 0 1.5 0.5 0.4

10% citric acid (n � 12) 9 3 0 1.3 0.6 7 4 1 1.5 0.6 1 9 2 2.0 0.5 0.0

Figure 1. Scanning electron microscopy photomicrographs of the root canal walls after final irrigation (original magnification�2,000). (A) The smear layer on the middlethird of a root canal in control group. (B) The smear layer was removed from the coronal third of a root canal in the SmearClear group, but dentinal tubules contained debris(amoderate smear layer). (C) Complete removal of the smear layer from themiddle third of a root canal in 17%EDTA group. All dentinal tubules are clean and open. (D) Thesmear layer has removed from the apical surface of a root canal in 10% citric acid group, but dentinal tubules contained debris (a moderate smear layer).

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moderate smear layer on the coronal, middle, and apical thirds(Fig. 1B). In EDTA and citric acid groups, no smear layer was detectedon the surface of most samples in the coronal and middle thirds, but amoderate smear layer was observed in the apical third of most roots inthese two groups (Figs. 1C and D). The comparison of the four groupsshowed that the canal walls in the SmearClear, EDTA, and citric acidgroups were significantly cleaner than in control group (p! 0.001).The comparison of remaining smear layer showed no significant differ-ences in the efficacy of SmearClear, EDTA and citric acid in smear layerremoval at the coronal (p� 0.110), middle (p� 0.191) and apical(p� 0.147) thirds of the root canals.

Comparison of three one thirds of the canals in each group showedno statistically significant difference in SmearClear, EDTA, and controlgroups (Table 1). But in the citric acid group, the efficacy of the che-lating agent was significantly less in the apical third of the samplescompared with the coronal (p � 0.007) and middle (p � 0.039)thirds.

DiscussionThe relevant literature shows a wide variety of irrigation times and

volumes of irrigants in removing the smear layer. To minimize destruc-tive effects on dentin reported by some investigators (10–13), we useda low volume (1 mL) of chelating agents for a short application time (1minute). The significant difference between control and the othergroups is in accordance with other studies that have shown that NaOClis not effective in removing the smear layer (10, 12, 23–25).

The current study showed that the process of smear layer removalwas more efficient in the coronal and middle thirds than in the apicalthird of the canals. This finding is in agreement with the results ofvarious studies that have shown an effective cleaning action in the coro-nal and middle thirds of the canals even when different irrigation timesand volumes of solutions were investigated (9, 10, 26, 27). A largercanal diameter in the coronal and middle thirds exposes the dentin to ahigher volume of irrigants, allowing a better flow of the solution and,hence, further improving the efficiency of smear layer removal (10, 27).

SmearClear is a 17% EDTA solution with two additional surfac-tants. Abou-Rass and Patonai (28) confirmed that reduction of surfacetension of endodontic solutions improved their flow into narrow rootcanals. Therefore, it may be speculated that the addition of two surfac-tants to EDTA should improve its penetration ability into narrowapical region of the root canal. However, the present study showedthat the surfactants in SmearClear did not improve its efficacy insmear layer removal compared with the surfactant-free EDTA. Thisresult is in agreement with the findings of Lui et al. (22) who used 5mL of SmearClear for 1 minute followed by 5 mL of 1% NaOCl as finalirrigants. Also, other studies have shown that the reduction of surfacetension of endodontic chelators did not improve their calcium chelatingability (18, 29).

The results of smear layer removal with 10% citric acid comparedwith 17% EDTA in this study are in agreement with those studies thatreported a minor or no difference in smear layer removal with citricacid and EDTA (20, 21, 30–32). In the current study, 1mL of 10% citricacid was used for 1minute. The significant difference between the apicalthird and the two other thirds of the root canals in citric acid group maybe related to the volume and/or application time of citric acid. It seemsthe application of higher volumes of citric acid over 1 minute improvesits efficacy in removing the smear layer. Accordingly, Sterrett et al. (33)showed that the effect of 10% citric acid on dentin demineralization wastime dependent at 1, 2, and 3minutes. Some investigators have reportedthat the application of 10% citric acid for more than 1 minute and in avolume more than 1 mL was more effective than 17% EDTA in terms of

decalcifying ability (15, 18). However, another study did not show anyrelation between decalcifying ability of these solutions and their effi-ciency in smear layer removal (34).

EDTA is an effective chelating agent for the removal of the smearlayer. However, the erosion of dentinal tubules caused by the applica-tion of EDTA over 1 minute and in a volume more than 1 mL has beenreported (10–13). Crumpton et al. (14) showed that the smear layerwas efficiently removed with a final rinse of 1 mL of 17% EDTA for 1minute followed by 3 mL of 5.25% NaOCl. But the present study showedthat this protocol was not efficient to completely remove the smear layer,especially in the apical third. Murray et al. (35) also showed that thesmear layer was not completely removed from all of the instrumentedroot canals by using %17 EDTA according to this protocol. Conse-quently, it is important to use othermethods, such as ultrasonic devices,for improving the efficiency of low-volume chelating agents used for ashort application time (22).

ConclusionBased on the results of this study, the application of 1 mL of

SmearClear, 17% EDTA, and 10% citric acid for 1 minute followed by 3mL of 5.25%NaOCl was not sufficient to completely remove the smearlayer, especially in the apical third. The addition of surfactants to EDTAin SmearClear did not result in better smear layer removal comparedwith EDTA alone.

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2. Mader CL, Baumgartner JC, Peters DD. Scanning electron microscopic investigationof the smeared layer on root canal walls. J Endod 1984;10:477–83.

3. Torabinejad M, Handysides R, Khademi AA, Bakland LK. Clinical implications of thesmear layer in endodontics: a review. Oral Surg Oral Med Oral Pathol Oral RadiolEndod 2002;94:658–66.

4. Örstavik D, Haapasalo M. Disinfection by endodontic irrigants and dressingsof experimentally infected dentinal tubules. Endod Dent Traumatol 1990;6:142–9.

5. White RR, Goldman M, Lin PS. The influence of the smeared layer upon dentinaltubule penetration by plastic filling materials. J Endod 1984;10:558–62.

6. Economides N, Liolios E, Kolokuris I, Beltes P. Long-term evaluation of the influenceof smear layer removal on the sealing ability of different sealers. J Endod1999;25:123–5.

7. Shahravan A, Haghdoost AA, Adl A, Rahimi H, Shadifar F. Effect of smear layer onsealing ability of canal obturation: a systematic review and meta-analysis. J Endod2007;33:96–105.

8. Yamada R, Aramas A, Goldman M, Lin PS. A scanning electron microscope compar-ison of a high volume final flush with several irrigating solutions. Part 3. J Endod1983;9:137–42.

9. Baumgartner JC, Mader CL. A scanning electron microscopic evaluation of four rootcanal irrigation regimens. J Endod 1987;13:147–57.

10. Torabinejad M, Khademi AA, Babagoli J, et al. A new solution for the removal of thesmear layer. J Endod 2003;29:170–5.

11. Calt S, Serper A. Time-dependent effects of EDTA on dentin structures. J Endod2002;28:17–9.

12. Torabinejad M, Cho Y, Khademi AA, Bakland LK, Shabahang S. The effect of variousconcentrations of sodium hypochlorite on the ability of MTAD to remove the smearlayer. J Endod 2003;29:233–9.

13. Tay FR, Gutmann JL, Pashley DH. Microporous, demineralized collagen matrices inintact radicular dentin created by commonly used calcium-depleting endodonticirrigants. J Endod 2007;33:1086–90.

14. Crumpton BJ, Goodell GG,McClanahan SB. Effects on smear layer and debris removalwith varying volumes of 17% REDTA after rotary instrumentation. J Endod2005;31:536–8.

15. Machado-Silveiro LF, González-López S, González-Rodríguez MP. Decalcification ofroot canal dentine by citric acid, EDTA and sodium citrate. Int Endod J2004;37:365–9.

16. Baumgartner JC, Brown CM, Mader CL, Peters DD, Shulman JD. A scanning electronmicroscopic evaluation of root canal debridement using saline, sodiumhypochlorite,and citric acid. J Endod 1984;10:525–31.

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17. Wayman BE, Kopp WM, Pinero GJ, Lazzari EP. Citric and lactic acids as root canalirrigants in vitro. J Endod 1979;5:258–65.

18. Scelza MF, Teixeira AM, Scelza P. Decalcifying effect of EDTA-T, 10% citric acid, and17% EDTA on root canal dentin. Oral Surg Oral Med Oral Pathol Oral Radiol Endod2003;95:234–6.

19. Czonstkowsky M, Wilson EG, Holstein FA. The smear layer in endodontics. Dent ClinNorth Am 1990;34:13–25.

20. Pérez-Heredia M, Ferrer-Luque CM, González-Rodríguez MP. The effectiveness ofdifferent acid irrigating solutions in root canal cleaning after hand and rotary instru-mentation. J Endod 2006;32:993–7.

21. Di Lenarda R, Cadenaro M, Sbaizero O. Effectiveness of 1 mol L-1 citric acid and 15%EDTA irrigation on smear layer removal. Int Endod J 2000;33:46–52.

22. Lui JN, Kuah HG, Chen NN. Effect of EDTA with and without surfactants or ultrasonicson removal of smear layer. J Endod 2007;33:472–5.

23. Garberoglio R, Becce C. Smear layer removal by root canal irrigants. A comparativescanning electron microscopic study. Oral Surg Oral Med Oral Pathol 1994;78:359–67.

24. Baumgartner JC, Cuenin PR. Efficacy of several concentrations of sodium hypochlo-rite for root canal irrigation. J Endod 1992;18:605–12.

25. Grandini S, Balleri P, Ferrari M. Evaluation of Glyde File Prep in combination withsodium hypochlorite as a root canal irrigant. J Endod 2002;28:300–3.

26. Abbott PV, Heijkoop PS, Cardaci SC, Hume WR, Heithersay GS. An SEM study of theeffects of different irrigation sequences and ultrasonics. Int Endod J 1991;24:308–16.

27. Teixeira CS, Felippe MC, Felippe WT. The effects of application time of EDTA andNaOCl on intracanal smear layer removal: an SEM analysis. Int Endod J 2005;38:285–90.

28. Abou-Rass M, Patonai FJ Jr. The effects of decreasing surface tension on the flow ofirrigating solutions in narrow root canals. Oral Surg Oral Med Oral Pathol1982;53:524–6.

29. Zehnder M, Schicht O, Sener B, Schmidlin P. Reducing surface tension in endodonticchelator solutions has no effect on their ability to remove calcium from instrumentedroot canals. J Endod 2005;31:590–2.

30. Goldman LB, Goldman M, Kronman JH, Lin PS. The efficacy of several irrigatingsolutions for endodontics: a scanning electron microscopic study. Oral Surg OralMed Oral Pathol 1981;52:197–204.

31. Takeda FH, Harashima T, Kimura Y,Matsumoto K. A comparative study of the removalof smear layer by three endodontic irrigants and two types of laser. Int Endod J1999;32:32–9.

32. Zehnder M, Schmidlin P, Sener B, Waltimo T. Chelation in root canal therapy recon-sidered. J Endod 2005;31:817–20.

33. Sterrett JD, Bankey T, Murphy HJ. Dentin demineralization. The effects of citric acidconcentration and application time. J Clin Periodontol 1993;20:366–70.

34. Scelza MF, Pierro V, Scelza P, Pereira M. Effect of three different time periods ofirrigation with EDTA-T, EDTA, and citric acid on smear layer removal. Oral Surg OralMed Oral Pathol Oral Radiol Endod 2004;98:499–503.

35. Murray PE, Farber RM, Namerow KN, Kuttler S, Garcia-Godoy F. Evaluation ofMorinda citrifolia as an endodontic irrigant. J Endod 2008;34:66–70.

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The Evaluation of Bond Strength of a Composite and aCompomer to White Mineral Trioxide Aggregate with TwoDifferent Bonding SystemsEmine Sen Tunç, DDS, PhD,* Isıl Saroglu Sönmez, DDS, PhD,† Sule Bayrak, DDS, PhD,* andTürkan Egilmez, DDS*

Abstract

The purpose of this study was to evaluate the bondstrength of a resin composite and a polyacid modifiedcomposite or “compomer” to white mineral trioxideaggregate (WMTA) with two different bonding systems(total-etch one bottle and self-etch one step). Fortyspecimens of WMTA were prepared and divided intofour groups. In group one, Single Bond (3M/ESPE, StPaul, MN) and Z250 (3M/ESPE) were placed overWMTA. In group two, Prompt L-Pop (3M Dental Prod-ucts, St Paul, MN) and Z250 were applied. In groupthree, Single Bond was applied with Dyract AP(Dentsply DeTrey, Konstanz, Germany), and, in groupfour, Prompt L-Pop was applied with Dyract AP. Theshear bond strength was measured, and the fracturedsurfaces were examined. The results of the shear bondstrength tests were analyzed by one-way analysis ofvariance test. The results of this study have suggestedthat the total-etch one-bottle adhesive system medi-ated a stronger bond to WMTA for both the resincomposite and the compomer investigated. The place-ment of composite (Z250) and compomer materials(Dyract AP), used with total-etch one-bottle adhesive(Single Bond), over WMTA as final restoration may beappropriate. (J Endod 2008;34:603–605)

Key Words

Compomer, composite resin, shear bond strength,white mineral trioxide aggregate

Mineral trioxide aggregate (MTA) is a biocompatible material with numerous ex-citing clinical applications in endodontics (1-3). MTA is a powder consisting of

fine hydrophilic particles of tricalcium aluminate, tricalcium silicate, and tricalciumoxide. It also contains small amounts of othermineral oxides, whichmodify its chemicaland physical properties (4, 5). In the presence of moisture, MTA sets into a hard massby forming calcium hydroxide and silicate hydrate gel (6). It is available commerciallyas ProRoot MTA (Dentsply; Tulsa Dental, Tulsa, OK) and has been proposed as apotential material for furcation repair, internal resorption treatment, pulpotomy pro-cedures, and capping of pulps with reversible pulpitis (2, 4, 7–12).

As the use of MTA in vital pulp therapy has gained popularity, the material thatwould be placed over MTA as final restoration is an important matter. The potential ofrestorative materials to attach to MTA is not well known. Until the initiation of this study,there were no published reports documenting the bond strength between MTA andrestorative materials. The aim of this study was to measure the bond strength of afrequently used resin composite (Z250; 3M/ESPE, St Paul, MN) and a polyacidmodifiedcomposite resin or “compomer” (Dyract AP; Dentsply DeTrey, Konstanz, Germany)when bonded to white MTA (WMTA) with two different bonding systems (one bottletotal etch and one step self-etch).

Materials and MethodsForty specimens of WMTA (Dentsply, Tulsa Dental) were prepared by using cylin-

drical acryl blocks. The blocks had central hole measuring 4mm in diameter and 2mmin depth. WMTA was mixed according to the manufacturer’s instructions. The acrylicblocks were filled with WMTA and covered with a wet cotton pellet and temporary fillingmaterial (Cavit; ESPE America, Inc, Norristown, PA). Then, the specimens were storedat 37°C with 100% humidity for 48 hours to encourage setting. After the removal of thetemporary material, the WMTA surface was not rinsed or polished. Specimens weredivided into 4 groups of 10 specimens.

Group One

TheWMTA surface was etched for 15 seconds with 37.5% phosphoric acid etchinggel (Kerr, Karlsruhe, Germany), rinsed with water for 10 seconds, and excess water wasremoved by blotting with absorbent paper, leaving the surface visibly moist dried. SingleBond (3M/ESPE) was then applied in 2 consecutive coats, gently air dried with oil-freecompressed air from an air syringe for 5 seconds to evaporate the solvent (keepingthe air syringe 2 cm from the surface), and light cured for 10 seconds. Resin com-posite Z250 was applied into a cylindrical shaped plastic matrix with an internal diam-eter of 2 mm and height of 2 mm and then light cured with a light-emitting diodelight-curing unit (Elipar Freelight II, 3M ESPE)with the intensity at 1,200mV/cm2 for 20seconds.

Group Two

The WMTA surface was dried for 10 seconds (keeping the air syringe 2 cm fromthe surface) to ensure a dry surface. Prompt L-Pop (3M Dental Products, St Paul, MN)was applied with scrubbing for 15 seconds. Then, the surface was gently air dried with

From the *Department of Pediatric Dentistry, University ofOndokuz Mayıs, Samsun, Turkey; and †Department of PediatricDentistry, Faculty of Dentistry, University of Kırıkkale,Kırıkkale, Turkey.

Address requests for reprints to Dr Isıl Saroglu Sönmez,Kırıkkale Universitesi, Dis Hekimligi Fakültesi, Pedodonti ABD,Kırıkkale, Turkey. E-mail address: isilsaroglu@yahoo.com.0099-2399/$0 - see front matter

Copyright © 2008 by the American Association ofEndodontists.doi:10.1016/j.joen.2008.02.026

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