hand files

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Hand files

Files are the instruments most used for cleaning and shaping the root canal system.

Traditionally they are manufactured from stainless steel in the form of a filamentwith a round cross-section and an ISO .02 Taper. They are firstly precision groundin such a way as to have a quadrangular cross-section and then twisted clock wiseto achieve the definitive form. The number of spirals per mm (pitch) for stainlesssteel files can very slightly depend on the manufacturers but is always more(generally double) than that of the reamers; their blades are furthermore positioned

perpendicular to the long axis of the instrument giving files a particularly efficientcutting action during filing (- CANTATORE, G.:Preparazionecanalare con

strumentimeccanici Ni-Ti. Dental Cadmos (Dossier). 2:11, 1996.- CANTATORE, G.: Evolution des techniques d¶instrumentationcanalaire.

European Dental Magazine Le Monde Dentaire. 87:11, 1998.- KRELL, K.V.: Endodontic instruments. In: Walton R.E., Torabi-nejad M. (eds.):

Principles and practice in endodontics. W.B. Saunders Company, Philadelphia. p.149, 1989.)

K FILES

The K-type file was first introduced in 1901 and receives the name K-type from theholder of its original patent, the Kerr Manufacturing Company.K-Files are made bytwisting a steel wire with a square cross-section. In cross-section a K-File has arobust quadrangular design which increases its resistance to torsion and flexionmaking it particularly useful in the initial negotiation of the canal; the four pointsof contact by the blades against the canal walls improve the tactile perception of theoperator, making the KFilethe ideal instrument for exploring (scouting) endodonticanatomy. The tip of the K-File is cutting and has an aggressive transition anglewith the first spiral capable of causing ledging especially when using the lessflexible instruments in curved canals. The K-Files produce large amounts of dentinal debris, which can block the spirals of the files making them less efficientat cutting and the push and pull action can push debris apically, causing a plug and

blocking the foramen.After having dominated the market for 65 years, K-style endodontic instrumentscame into a series of modifications beginning in the 1980s.

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Modifications of K- style files

K- flex files

The Kerr Manufacturing Company in 1982 introduced a new instrument designthat they termed the K-Flex File (Sybron Endo/Kerr; Orange Calif.). Itrepresentsthe first attempt to make a ³hybrid´ instrument, able to integrate the force andversatility of a K-File with the cutting aggression of a Hedstroem file.The cross-section of the K-Flex is rhombus or diamond shaped. The spirals or flutes are

produced by the same twisting procedure used to produce the cutting edge of thestandard K-type files; however, this new cross-section presents significant changesin instrument flexibility and cutting characteristics. The cutting edges of the highflutes are formed by the two acute angles of the rhombus and present increasedsharpness and cutting efficiency. The alternating low flutes formed by the obtuse

angles of the rhombus are meant to act as an auger, providing more area for increased debris removal. The decreased contact by the instrument with the canalwalls provides a space reservoir that, with proper irrigation, further reduces thedanger of compacting dentinal filings in the canal.Testing five brands of K-type files for stiffness, the San Antonio group found K-Flex files to be the most flexible. Moreover, not a single K-Flex fractured in torquetesting, even when twisted twice the recommended level in the ADAspecification. (Roth WC, et al. A study of the strength of endodontic files. JOE 1983;9:228.)

K- flexo files

The K-Flexofiles (www.dentsply-maillefer.com) are files in steel obtained bytwisting a wire with a triangular cross-section. The FlexoFiles tip is rounded andhas a transitional angle that is blunted making this instrument safer during theshaping of curved canals and particularly suited for the balanced force technique.(POWELL, S.E., SIMON, J.H.S., MAZE, B.B.: A comparison of the effect of modifyed and nonmodified instrument tips on apical canal configuration. J. Endod.12:293, 1986.- POWELL, S.E., WONG, P.D., SIMON, J.H.S.: A comparison of the effect of

modified and nonmodified instrument tips on apical canal configuration. J. Endod.14:224, 1988.)They have a triangular cross-section which helps them to maintain a 3 pointcontact with the dentinal wall, at the same it; it makes the files less bulky and moreflexible than conventional K-files.Furthermore, the increased space for the removal

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of debris (due to the triangular design in cross-section) explains why there is lesstendency with respect to K-Files to build dentin mud andto cause dangerous apical

plugging with debris .( - NEWMAN, J.C., BRANTLEY, W.A., GERSTEIN, H.: A study of the cutting efficiency of seven brands of endodontic files in linear motion. J. Endod. 9:136, 1983.)The FlexoFiles are only available in ISO diameters of 0.15 to 0.40 mm and lengths21, 25 and 31 mm.The K-FlexoFiles Golden Mediums (www.dentsplymaillefer.com ) are identical tothe K-FlexoFiles exceptthat the diameters have intermediate values comparedtothose of the ISO standard.The K-FlexoFiles Golden Mediums infact areonlyavailable in ISO diameters 12, 17, 22, 27, 32 and 37.

Tr iple - flex file

Kerr has introduced a hybrid instrument they call the Tr iple-Flex File (Ke rr; O ra nge,C a lif.) It has more spiral flutes than a K reamer but fewer than a K file.Made from triangular stainless steel and twisted, not ground, the companyclaims the instrument is more aggressive and flexible than the regular K-styleinstruments.

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SA- K-file, B- K-reamer, C- K-flex file, D- triple flex file

hand files

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