Self-Adjusting File SAF Review

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Review Article Int Dent Res 2011;1:18-25

18 IDR Volume 1, Number 1, 2011

A Literature Review of Self Adjusting File

zkan ADIGZEL Assistant Professor, Dicle University, Faculty of Dentistry, Department of Operative Dentistry and Endodontics, Diyarbak r,TURKEY

Key WordsSelf-adjusting file, new rotaryfile, nickel-titanium, endodonticfiles

Correspondence:zkan ADIGZELDicle University,Faculty of Dentistry,Department of Operative Dentistryand Endodontics,21280, Diyarbakir, TURKEY.e-mail:[email protected]

Abstract A primary aim of root canal treatment is to completely clean and

shape the root canal system. Various instruments are available forendodontic instruemntation. Although rotary systems do preparemany canals without major procedural errors, they do not addresscanal types with long-oval or flat cross sections. A newly developedself-adjusting file (SAF) was designed to address the shortcomings of traditional rotary files by adjusting itself to the canal cross section.This instrument consists of a compressible opened NiTi tube that, onplacement into a root canal, will exert pressure against the canalWall. The SAF is used in an in-and-out motion powered by ahandpiece and under constant irrigation.

The aim of this review was to describe instrument design, usageparameters and features of Self Adjusting File.

(Int Dent Res 2011;1:18-25)

IntroductionThe cleaning and shaping of the root canal

system is an important objective of root canaltreatment (1,2). Original root canal path should bemaintained and the root canal wall dentin should becut circumferentially so that prepared root canal wall

outline reflects the original outline (1). The goal of instrumentation is to provide a continuously taperedpreparation that maintains original root canalanatomy, keeping the foramen without any ledgeand transportation from the original canal curvature(3,4).

A variety of instruments are available for theroot canal instrumentation. For many years, handfiles are the most commonly used for endodonticinstruments (5). Traditionally, this group of instruments has been manufactured from stainlesssteel and comprises two basic designs, the K-typeinstruments (K-files and K-reamers) and theHedstrom file (5, 6). Although almost all theseinstruments were designed between many years

ago, important changes have introduced in recentyears with regard to their quality, efficacy, andstandardization (7). Nickel-titanium instruments formanuel and rotary use have been developed duringthe last decade (8). It was introduced to facilitateroot canal instrumentation (8).

Nickel-Titanium Rotary Instruments

Since the early 1990s, several endodonticinstrument systems manufactured from nickel-titanium have been introduced into endodontic clinicpractice. The specific design characteristics vary,such as tip sizing, taper, cross section, helix angle,and pitch. To date, several devices and methodshave been used to perform endodontic treatment.The specific design characteristics vary, such as tipsizing, taper, helix angle, cross section (Fig. 1) (9),and pitch. New designs continually are produced (9).


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Adgzel Self-Adjusting File - Review

International Dental Research 2011 23

During the operating procedure, the SAF isinserted into the root canal while vibrating and ismeticulously pushed in until it reaches the measuredworking length. The SAF file is operated in twocycles of 2 minutes each for a total of 4 minutes per

canal. It is performed with in-and-out manualmotion and with continuous irrigation VATEAIrrigation Device, in this way allowing continuousfresh irrigant to be present in the canal during theprocedure. This procedure is reported to remove auniform dentin layer 60- to 75-mm thick from theroot canal circumference. The SAF is removed fromthe canal for inspection after each cycle. Each SAFfile is designed and recommended for single use(14).

During the first minute of each cycle of 2minutes, sodium hypochlorite (3%) is used as theroot canal irrigant and EDTA (17%) is used duringthe second minute. The flow rate of the irrigants setat 5 mL/min, resulting in a total volume of 10 mL of each irrigant used during the procedure withadditional activation of the irrigant by its vibratingmotion. After two cycles, an additional irrigation withEDTA (17%) is used for 0.5 minutes with thevibrational mechanism turned off followed by a finalshort flush with sodium hypochlorite (3%, 5 mL) toremove the remaining EDTA (14).

Mechanical Analysis of SAF

Compressibility of the SAF force applied as aresult of compression, surface roughness, abrasivitytest, durability (torque test, ada cyclic fatigue test,free buckling fatigue test, functional fatigue-to-failure test), SAF degradation as a function of working time and irrigation experiments mechanicalanalysis tests were conducted as previously reportedby Hof et al.(15). It can be summarized as follows(15):

a. The SAF file may be elasticallycompressed considerably from adiameter of 1.5 mm to dimensionsresembling those of an ISO # 20 K-filebecause of the special design of the file.

b. The SAF file creates circumferentialforce when initially compressed.

c. The rough surface, combined with theforce and the in-and out vibrationalmechanism, allows for the removal of dentin by filing.

d. The circumferential force and the abilityto remove dentin decreases as the

diameter of the canal enlarges.e. If the file is reused, the ability toremove dentin declines.

f. The SAF file is mechanically durable forcontinuous operation for 29 minutes.

g. SAF application does not push theirrigant beyond the apical foramen.

Removal of the Smear Layer in the Apical Part of the Cana l

Debridement of the root canal system isimportant for endodontic success (16). Irrigantsmust be brought into direct contact with the entireroot canal wall for optimal effectiveness and it wasreported that enhancement of the flushing action isessential to improve root canal cleanliness (17, 18).

As with any endodontic instrument, the SAFproduces a smear layer on the root canal walls (19).

This layer should be removed in order to provide thepenetration of intracanal disinfectant into thedentinal tubules and also the complete adaptation of obturation materials to the dentin walls (17).

Although sodium hypochlorite has beenrecommended as the main irrigant, it can notdissolve inorganic dentin particles (17). Irrigationwith NaOCl in association with a chelating agentsuch as ethylenediaminetetraaceticacid (EDTA) citricacid have been recommended in endodontic therapy(17). Studies have shown that debris can remain inthe root canal system after instrumentation andirrigation. However, scanning electron microscopicstudies show that the removal of the smear layerand debris in the apical third of the root canal usingeither a syringe and a needle or a chelating agentleaves much to be desired (19). It was reported thatwhen 3% sodium hypochlorite and 17% EDTA wereused as irrigants with the SAF file, the root canalwall (including its apical third) was rendered clean of debris and the smear layer (19). It might beattributed to effective continuous substitute of thechelator in the apical third and to the mechanicalvibrating action of the SAF in this region (14).

Root Canal Obturation of SAF-prepared root canals

Obturation of the root canal system has beenperformed using various techniques. Obturation of SAF-prepared root canals might be possible done byany of the obturation methods. Obturation usinglateral compaction using chloroform-dippedcustomized master cones is reported. This techniquehas the advantage of providing visualize the shapeof the SAF-treated root canals (14). Metzger et alreported that the self-adjusting files showed better


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Self-Adjusting File - Review Adgzel

24 IDR Volume 1, Number 1, 2011

cleaning and shaping and better adaptation of theroot canal filling material (20).

Clinical Use

A series cases with SAF treatment have been

completed according to protocol as described byMetzger et al (14). It was reported in more than 100clinical cases without any file seperation (14).

ConclusionsThe usage new concept of rotary nickel-

titanium files adds a new quality to root canalpreparation. SAF operated with continous flow of irrigation results in debris and smear free in most of the root canal walls. The SAF represents a newapproach in endodontic rotary file design andoperation. It contributes greatly to endodonticarmamentarium. Its main features are as follows(14, 15, 19):

1. The SAF file is different from any nickel-titanium rotary file. It is claimed to adapt itself three-dimensionally to the shape of the root canal,including to adapt to its cross-section

2. One file is used during the procedure.3. Canal straightening and canal transportation

of curved canals are largely denied because of thelack of a rigid metal core.4. High mechanical durability overcomes the

mechanical failure of nickel-titanium instruments.5. Hollow and flexible design allows continuous

irrigation with constant refreshment of the irrigantthroughout the procedure.

6. SAF file generates circumferential force.7. It tends to keep the apical part of curved

canals closer to its original location with no zipping.8. SAF application with continuous irrigation

does not push the irrigant beyond the apicalforamen.

References

1. Baugh D, Wallace J. The Role of ApicalInstrumentation in Root Canal Treatment: AReview of the Literature J Endod,2005;31(5):333-340

2. Bartha T, Kalwitzki M, Lst C, Weiger R.Extended apical enlargement with hand filesversus rotary NiTi files. Part II. Oral Surg

Oral Med Oral Pathol Oral RadiolEndod. 2006 Nov;102(5):692-7.

3. Carvalho LA,, Bonetti I, Aurelio M, Borges G. A comparison of molar root canal preparation using stainless-steel and nickel-titaniuminstruments. Journal of Endodontics,1999;25(12):807-10

4. Matwychuk M, Bowles W, McClanahan S,Hodges J, Pesun I. Shaping abilities of two

different engine-driven rotary nickel titaniumsystems or stainless steel balanced-forcetechnique in mandibular molars. JEndod. 2007;33:868871.

5. Walton RE, Torabinejad M. Principles andPractice of Endodontics. 2nd ed.Philadelphia, PA: Saunders; 1996.

6. Wein FS. Endodontic Therapy. 5th ed. StLouis, MO: Mosby; 1996.

7. Leif Tronstad. Clinical Endodontics, ATextbook.. 2nd ed. Thieme, New York; 2003.

8. Yoshimine Y, Ono M, Akamine A. Theshaping effects of three nickel-titaniumrotary instruments in simulated S-Shapedcanals. J Endod 2005;31:373-5.

9. Hargreaves KM, Cohen S. Patways of thepulp. 6th ed. Mosby, 2006.

10. Wu M-K, Wesselink PR. A primaryobservation on the preparation andobturation in oval canals. Int Endod J2001;34:13741.

11. Yao JH, Schwartz SA, Beeson TJ. Cyclicfatigue of three types of rotary nickel-titanium files in a dynamic model. J Endod2006;32:557.

12. Peters OA, Paque F. Current developments inrotary root canal instrument technology andclinical use: a review. Quintessence Int.2010 Jun;41(6):479-88. Review.

13. Ersev H, Y lmaz B, iftiolu E, zkarsl F. Acomparison of the shaping effects of 5nickel-titanium rotary instruments insimulated S-shaped canals. Oral Surg OralMed Oral Pathol Oral Radiol Endod2010;109:e86-e93

14. Metzger Z, Teperovich E, Zary R, Cohen R,Hof R. The self-adjusting file (Saf). Part 1:Respecting the root canal anatomy - a newconcept of endodontic files and itsimplementation. J Endod 2010;36:67990.

15. Hof R, Perevalov V, Eltanani M, Zary R,

Metzger Z. The self-adjusting file (Saf). Part2: mechanical analysis. J Endod2010;36:69196.Sdf

16. Siqueira JF Jr, Rocas IN. Clinical implicationsand microbiology of bacterial persistenceafter treatment procedures. J Endod2008;34:1291301.

17. Zehnder M. Root canal irrigants. J Endod2006;32:38998.

18. Rdig T, Dllmann S, KonietschkeF, Drebenstedt S, Hlsmann M. Effectivenessof different irrigant agitation techniques ondebris and smear layer removal in curvedroot canals: a scanning electron microscopystudy. J Endod. 2010;36(12):1983-7.

19. Metzger Z, Teperovich E, Cohen R, et al. TheSelf-adjusting File (SAF). Part 3: Removal of


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Debris and Smear LayerA ScanningElectron Microscope Study. J Endod2010;36:697702.

20. Metzger Z, Zary R, Cohen R, TeperovichE, Paqu F.The quality of root canalpreparation and root canal obturation incanals treated with rotary versus self-

adjusting files: a three-dimensional micro-computed tomographic study. JEndod. 2010;36(9):1569-73.

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