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SUMMARY:The aim of this in vitro study was to establish and

compare the amount of debris and irrigant extruded apicallyafter root canal preparation with two rotary systems (K3 andRaCe).

Methods: Two groups of 24 extracted teeth withsingle canals were used. In group 1 (12 teeth) the root canalswere instrumented using nickel-titanium K3 rotaryinstruments and “crown-down” technique. In group 2 (12teeth) the root canals were instrumented using nickel-titanium RaCe rotary instruments and “crown-down”technique. Debris and irrigant extruded from the apicalforamen were collected into pre–weighed vials (using Myersand Montgomery technique) and the amounts weredetermined. Time taken for each instrumentation techniquewas also determined. The data was input and processedusing the statistical software package SPSS 17.0.1.

Results: The amount of the debris extruded throughapical foramen in group 1 (K3 files) was 0,225 mg and ingroup 2 (RaCe files) was 0,213 mg. The volume of theextruded irrigant was 0,247 ml in group 1 and 0,238 ml ingroup 2. Time taken for instrumentation was 8.3 min byRaCe files and 8.7 min by K3 files. The difference in theamount of debris and irrigant produced among two groupswas not significant.

Conclusions: It was concluded that the RaCe systeminduces less extruded debris and irrigant through the apicalforamen, than the K3 system. The difference between twogroups was not significant.

Key words: apical extrusion, K3 nickel-titaniuminstruments, RaCe nickel-titanium instruments, rotaryendodontic systems

INTRODUCTIONApical extrusion of debris and irrigant during

cleaning and shaping of the root canal is one of the commonproblems encountered by an endodontist. Several studieshave shown that dentin fillings, necrotic tissue, pulpremains, microorganisms and irrigating solution may beforced towards the periapical tissues during root canalinstrumentation [1 - 8].

Apically extruded debris contributes to the severityof inflammation reaction. Tissue reactions followinginstrumentation shorter than the apex are milder than thosereactions that follow instrumentation beyond the apex.Therefore, minimizing the amount of apically extruded

debris should minimize postoperative reactions [9].Instrumentation methods, file size, and file type can

also have an effect. Researchers have observed that the filemay act as a plunger in the canal. Various studies useddifferent techniques for debris collection and theirmeasurement. Most recent studies used a more standardizedand replicable method. Myers and Montgomery (1991) werethe first to evaluate a manual rotary technique, comparingCanal Master (hand instruments) with conventional handfiling techniques.

Nowadays, there are a lot of rotary instruments. Theyare available in various designs [10 - 12].

The aim of this in vitro study was to establish andcompare the amount of debris and irrigant extruded apicallyafter canal preparation with two rotary systems (K3 andRaCe).

MATERIALS AND METHODSTwenty four extracted teeth with single canals were

used. All teeth had similar root curvatures of 0-10 degrees.The external surface of all teeth was cleaned with aperiodontal curette. All teeth were controlled with digitalradiographs in buccal and proximal directions to check fora single canal and one apical foramen. The teeth were storedin physiological saline solution.

The teeth crowns were cut at the CEJ and the lengthwas standardized to 15 mm. The pulp tissue was removedwith the help of broach.The working length was determinedwith electronic apex-locating device Raypex-5 (fig.1). Allof theteeth were instrumented by a single practitioner.

COMPARATIVE STUDY OF APICALLY EXTRUDEDDEBRIS AND IRRIGANT AFTER USING TWOROTARY SYSTEMS (K3, RACE)

Elka N. Radeva, Radosveta I. Vassileva,Department of Conservative dentistry, Faculty of Dental Medicine, MedicalUniversity - Sofia, Bulgaria

Journal of IMAB - Annual Proceeding (Scientific Papers) 2014, vol. 20, issue 1ISSN: 1312-773X (Online)

http://dx.doi.org/10.5272/jimab.2014201.459

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Fig. 2. Experimental model for collecting debris andirrigant during root canal preparation.

The teeth were divided into two experimental groupsof 12 teeth.

Group 1: Crown down engine-driven technique -nickel-titanium RaCe rotary instruments (FKG,Switzerland)

In the coronal part - taper.08.06/25 - ½ of a working length.06/20 - between ½ and 2 / 3 of working length.04/20, .04/25, .04/30, 04/35 – full working lengthAfter using each instrument the root canal was

irrigated with distilled water. Distilled water was used as theirrigant solution. Each canal was irrigated with total 10 mlof distilled water applying 27G 3/4½ (0.4×19 mm) needles.

Group 2: Crown down engine-driven technique -nickel-titanium K3 rotary instruments (Sybron Endo,USA)

In the coronal part - taper.08.06/25 - ½ of working length.06/20 - between ½ and 2/3 of working length.04/20, .04/25, .04/30, .04/35 – full working lengthAfter each applied instrument the root canal was

irrigated with distilled water. Each canal was irrigated with10 ml of distilled water in total applying 27G 3/4½ (0.4×19mm) needle. Distilled water was used to avoid any possibleweight increase due to NaOCl crystal formation. Controlgroup - five vials of distilled water were used as a control,which were dried the same way and weighed. Time takenfor each instrumentation technique was also determined.

Debris and irrigant extruded from the apical foramenduring instrumentation were collected into vials (using theMyers and Montgomery technique) and the amounts weremeasured (fig.2).

The experimental model consists of two glass vials,one of them is larger and the other one is smaller (thesmaller one is inside the larger one - separate vials). Thelarge vial was closed with a rubber plug, which is piercedand the opening corresponds to the root diameter of thetooth. The root of the tooth is placed in this opening andthe surface is sealed with plastic.

During the processing of the root canals irrigant anddebris passed through the apical foramen are collected in asmall glass vial. This vial contains distilled water, and theapical part of the root is immersed in it. All vials werenumbered and measured by the quantity of distilled waterin them prior to the root canal processing.

Immediately after the canal instrumentation thesmaller vials are removed from the big one and measured.Then they are placed in an electric oven at a temperatureof 50-60° for 12-24 hrs until the liquid has evaporated (fig.3). All tubes with vaporized liquid are placed in a desiccatorcontaining CaCl2 in order to prevent absorption andmeasured three times with analytical balance. The averageof the measured values has been taken into considerationfor the final result.

Measurements were done with an analytical balancewith indication of the scale accurate to fifth place.

The data was input and processed using the statisticalsoftware package SPSS 17.0.1. The level of significance forrejecting the null hypothesis was fixed at p<0,05.

Fig. 1. Electrometric determination of working lengthwith Raypex-5.

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RESULTSThe amount of the debris extruded through apical

foramen in group 1 (RaCe files) was 0,213 mg (table 1 andfig.4) and in group 2 (K3 files) was 0,225 mg

The volume of the extruded irrigant was 0,238 ml ingroup 1 and 0,247 ml in group 2 (fig. 5).

Time taken for instrumentation was 8, 3 min by RaCefiles and 8, 7 min by K3 files (fig. 6).

The difference in the amount of debris and irrigantproduced among two groups was not significant.

Table 1. Weight of dry debris and irrigant extruded apically during shaping and cleaning by each rotary system

n-number of samplesX - arithmetic mean of the amount of extruded debris and irrigantSD – standard deviation

Crown-down techniqueIndex RaCe files (n=12) K3 files (n=12)

SD SDExtruded debris (mg) 0,213 0,020 0,225 0,079Extruded irrigant (ml) 0,238 0,020 0,247 0,098Time taken for instrumentation (min) 8,300 0,670 8,700 0,675

Fig. 4. Average extruded debris with RaCe file and K3 file.

Fig. 3. Dry substance after distilled water evaporationand moisture.

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Fig. 5. Average extruded irrigant with RaCe file and K3 file.

Fig 6. Average time taken in both rotary systems of canal instrumentation.

DISCUSSIONOur results showed a better performance of the crown

down technique with RaCe instruments compared to the K3files. All movements of the file used in this study wererotational. Rotation during instrumentation tended to packthe dentinal debris into the flutes of the files and directedthem toward the orifice. According to studies,instrumentation with the rotary systems could reduce theamount of debris extrusion to the periapical area [10, 11,5, 13, 14].

In group 1, a crown-down technique is used by theRaCe files. Despite being a .04 taper instrument, theextrusion of debris is due to its typical instrument design.

Easy RaCe (FKG, Switzerland) are Ni-Ti instruments withalternating cutting edges. These files implement morecutting dentin than scraping. They have a safe peak with atriangular cross-section. They have two cutting edges - thefirst is switched to a second, which is arranged at a differentangle and a cutting body with a length of 8 mm, whichallows varying helical angle and a variable angle ofinclination. This increases the files’ “antiscrewing”characteristics. The presence of the protective disc is an easyand convenient method for monitoring the metal fatigue.Files are used at 500 rev. / min. During the processing withmachine instruments dentine debris accumulated in thegrooves of the files, and then they go directly to the orifice.

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Address for correspondence:D-r Elka Radeva, PhDDepartment of Conservative dentistry, Faculty of Dental Medicine, MedicalUniversity - Sofia,1, G. Sofiyski blvd., 1431 Sofia, Bulgaria.e-mail: eliradeva@abv.bg;

32(9):665-671. [PubMed]11. Ferraz CC, Gomes NV, Gomes

BP, Zaia AA, Teixeira FB, Souza-FilhoFJ. Apical extrusion of debris andirrigants using two hand and three en-gine-driven instrumentation techniques.Int Endod J. 2001 Jul;34(5): 354-8.[PubMed] [CrossRef].

12. Jodway B, Hülsmann M. A com-parative study of root canal preparationwith NiTi-TEE and K3 rotary Ni-Ti in-struments. Int Endod J. 2006Jan;39(1):71-80. [PubMed] [CrossRef]

13. Leonardi LE, Atlas DM, RaidenG. Apical extrusion of debris by manualand mechanical instrumentation. BrazDent J. 2007; 18(1):16-9. [PubMed][CrossRef]

14. Zarrabi MH, Bidar M,Jafarzadeh H. An in vitro comparativestudy of apically extruded debris result-ing from conventional and three rotary(Profile, Race, FlexMaster) instrumen-tation techniques. J Oral Sci. 2006Jun;48(2):85-8. [PubMed] [CrossRef]

15. Radeva EN, Vassileva RI,Belcheva MD. In vitro study of apicallyextruded bacteria after two instrumen-tation techniques. Dental medicine,2011, 93 (1):19-23. [in Bulgarian]

REFERENCES:

Acknowledgments:This study was performed under contract No.5/27.07.2009 by the Medical University- Sofia.

In group 2, a crown-down technique is used by theK3 files. Despite being a .04 taper instrument, the extrusionof debris is due to its typical instrument design: positive rakeangle provides the active cutting action of the K3 endo files,wide radial land provides blade support while addingperipheral strength to resist torsional and rotary stresses, thethird radial land of K3 files stabilizes and keeps theinstrument centered in the canal and minimizes overengagement, radial land relief reduces friction on the canalwall.

The present results are also in accordance with thosereported by other authors who demonstrated a lower extrudeddebris, irrigant and bacteria using rotary Ni-Ti files [9, 15].

In the in -vitro studies the tooth is suspended in the

air or vacuum, but in vivo it is surrounded by periapicaltissues.

Obviously, one of the aims of canal preparationshould be to minimize apical extrusion in order to preventunwanted pain and inflammation. Using instruments andtechniques which minimize this extrusion of debris andirrigant during the root canal preparation is recommendable.

CONCLUSIONSIt was concluded that the RaCe system induces less

extruded debris and irrigant through the apical foramen thanthe K3 system. Processing time for root canal shaping withRaCe files was less than K3 files. The difference betweentwo groups was not significant.

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7. Vansan LP, Pecora JD, da CostaWF, Silva RG, Savioli RN. Comparativein vitro study of apically extruded ma-terial after four different root canal in-strumentation techniques. Braz Dent J.1997; 8(2):79-83. [PubMed]

8. Tanalp J, Kaptan F, SertS, Kayahan B, Bayirl G. Quantitativeevaluation of the amount of apically ex-truded debris. Using 3 different rotaryinstrumentation systems. Oral SurgOral Med Oral Pathol Oral Rad Endod.2006 Feb;101(2):252-259. [PubMed][CrossRef]

9. Hinrichs RE, Walker WA 3rd,Schindler WG. A comparison ofamounts of apically extruded debris us-ing handpiece-driven nickel-titaniuminstrument system. J Endod. 1998 Feb;24(2):102-106. [PubMed] [CrossRef]

10. Bidar M, Rastegar AF, GhazianiP, Namazikhah MS. Evaluation ofapically extruded debris in conventionaland rotary instrumentation techniques.J Calif Dent Assoc. 2004 Sep;