K files ..... king of cleaning in brief :)

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1. Files

–        mostly used for cleaning and shaping the root canal system.

–        They are firstly precision ground in such a way as to have a quadrangular cross-section and then twisted clock wise to achieve the definitive form.

–        The number of spirals per mm (pitch) for stainless steel 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 efficient cutting action during filing.

–        The first files to be marketed were the K-Files; many other instruments were introduced which can be differentiated from the traditional files by the manufacturing alloy used (NiTi instead of stainless steel), by the design of the cross-section and the tip, by the type of handle and length of shaft.

–        To optimize the cutting capability of the K-Files it is necessary to place the file in the canal in contact with the dentine walls and use a push and pull motion that should not range over more than 2 to 3 mm distance.

–        When the canal is elliptical in cross-section or even circular and larger than the File width, it is obvious that the instrument cannot be in contact with the whole circumference and over the whole length at the same time. Therefore, the instrument has to be reinserted more often and placed against the various parts of the canal circumference carrying out a so called “circumferential filing” of the walls.

–        In alternative to the filing movement the K-Files can be used by rotating them in the canal in a clockwise direction (watch-winding according to Ruddle) or by using Roane’s balanced forces technique: a 90° clock-wise rotation (engaging) during insertion, followed by a 360° counter-clockwise rotation (cutting) keeping the instrument at the same depth, and the final 90° clock-wise rotation during removal of the instrument (disengaging).

1.a K-Files

–        most used endodontic instruments.

–        K-Files are made by twisting a steel wire with a square cross-section. In cross-section a K-File has a robust quadrangular design which increases its resistance to torsion and flexion making it particularly useful in the initial negotiation of the canal; the four points of contact by the blades against the canal walls improve the tactile perception of the operator, making the K-File the ideal instrument for exploring (scouting) endodontic anatomy.

–        The tip of the K-File is cutting and has an aggressive transition angle with the first spiral capable of causing ledging especially when using the less flexible instruments in curved canals. The K-Files produce large amounts of dentinal debris, which can block the spirals of the files making them less efficient at cutting and the push and pull action can push debris apically, causing a plug and blocking the foramen.

–        To prevent this inconvenience, the file should principally work on withdrawal, the debris must be frequently rinsed away and their use must be alternated with frequent and abundant irrigation. The filing movement of the K-Files inside the canal must be quite gentle to prevent the instrument from being a plunger of dentin mud.

–        The K-Files are available in ISO diameters from .06 to .140 mm and lengths from 21, 25, 28, 30 and 31 mm.

1.b K-Flex

–        The K-Flex file (www.kerrdental.com) represents the first attempt to make a “hybrid” instrument, able to integrate the force and versatility of a K-File with the cutting aggression of a Hedstroem file.

–        The K-Flex has a rhomboidal cross-section, which increases the flexibility of the larger diameters, alternating depths of spirals capable of removing more debris and a reduction of 37,5% of the cross section area.

–        It is only available in stainless steel with the same diameters and lengths as K-Files.

1.c K-FlexoFiles

–        The K-Flexofiles (www.dentsply-maillefer.com) are files in steel obtained by twisting a wire with a triangular cross-section and is available from a diameter of 15.

–        Compared to the classic K-Files, the K-FlexoFiles differ  regarding the tip and cross-section.

–        The FlexoFiles tip is rounded and has a transitional angle that is blunted making this instrument safer during the shaping of curved canals and particularly suited for the balanced force technique.

–        The triangular section is less bulky than K-Files, increasing the flexibility of the FlexoFiles, while the three angles of contact that the blades have with the dentinal walls reduce the friction and favour penetration in an apical direction.

–        Furthermore, the increased space for the removal of debris (due to the triangular design in cross-section) explains why there is less tendency with respect to K-Files to build dentin mud and to cause dangerous apical plugging with debris.

–        The FlexoFiles are only available in ISO diameters of 0.15 to 0.40 mm and lengths 21, 25 and 31 mm.

–        Practically identical to the FlexoFiles are the Flexicut Files (www.antaeos.de). They are available in the same diameters and lengths as the FlexoFiles.

1.d K-FlexoFiles Golden Mediums

–        The K-FlexoFiles Golden Mediums (www.dentsply-maillefer.com) are identical to the K-FlexoFiles except that the diameters have intermediate values compared to those of the ISO standard.

–        The K-FlexoFiles Golden Mediums infact are only available in ISO diameters 12, 17, 22, 27, 32 and 37; the lengths remain those of the classic Maillefer 21, 25 and 31 mm.

–        Their use is recommended for long and calcified or curved canals where the passage from a 10 file to a 15 file or from a 15 to a 20 may be difficult; the use of intermediate diameters enable the operator to reach the working length earlier and with less risk of complications.

1.e Unifile

–        The Unifile (www.dentsply-maillefer.com) has a cross-section in the shape of an S obtained by machining a double helix on the long axis of a round wire.

–        The structure of the spirals show that Unifiles are not obtained by torsion but by micromachining like the Hedstroem files; the depth of the spirals is however less than that of the H-File with consequently higher strength.

–        The Unifiles are available in the ISO diameters from 15 to 80 and with lengths 21, 25 and 31 mm.

–        There is also a rotary version in stainless steel, available though only with lengths 21 and 25 mm.

1f. S-File

–        The S-File (www.sdidirecta.com) is obtained by micromachining a nickel titanium wire with ISO .02 taper having a S configuration in cross-section similar to a Unifile that however differs, due to a constant angle of the spirals throughout its working length and a spiral depth which increases from the tip to the handle.

–        Apart from the manual version, available in the ISO diameters from 15 to 80 and lengths 21, 25 and 28 mm, there is also a rotary version only available in lengths 21 and 25 mm.

1g. Flex-R

–        The Flex-R file (www.dentnetkorea.com), designed by Roane,characterized by a tip design that is completely modified.

–        According to Roane the tendency by conventional files to cause transportation of canals, ledges and perforations depends on their lack of flexibility, their cutting tip and their use with unbalanced forces.

–        Removing a section of the tip and eliminating all the cutting angles, it was possible to reduce the angle of the tip from 75° to 35° creating a type of collar that guides the penetration of the file.

–        Furthermore the spirals of the Flex-R files are obtained by micromachining and not by torsion and varies in depth according to the size of the instrument: less depth in the smaller sizes to give more strength and more depth in the bigger sizes to give more flexibility.

1.h Nitiflex

–        The Nitiflex (www.dentsply-maillefer.com) are files in nickel titanium with a rounded non-cutting tip, obtained by micromachining a round wire.

–        The Nitiflex are available in ISO diameters 15 to 60 and lengths of 21 and 25 mm.

–        They have a cross-section design that varies progressively with the size of the instruments with the aim of maintaining constant flexibility and torsional strength.

–        Infact the Niti with the smaller size are more fragile, have a core design that is triangular with convex sides to increase the mass of metal and thus the torsional strength

–        Large sizes are more robust but more rigid and have a triangular design with concave sides to increase flexibility .

1.k ProFile Series 29.02 Hand Files

·         The ProFile Series 29.02 Hand Files (www.tulsadental.com) are files manufactured by micromachining a steel or nickel titanium wire with .02 taper and is characterized by a tip with a rounded transition angle that reduces the risk of creating ledges in curved canals.

·         The ProFile Series 29 does not follow the standardization of the ISO diameters, but those of the ProFile 29 devised by Schilder in 1989: their diameter at the tip does not increase in a linear and fixed way but by 29.17%, enabling the operator to have more instruments in the range of maximum utility, (from size 10 to size 40).

·         Even the numbering of the ProFiles 29 does not follow the standard ISO system: infact they are numbered from 2 (with a tip diameter of 0.129 mm) to number 11 (with tip diameter 1.293 mm).

·         Furthermore there are ProFile 29 Hand files in steel number 00, 0 and 1 corresponding respectively to ISO files 06, 08 and 10. It is important to emphasize once again that the term ProFile 29 does not refer to a type of instrument but to a type of standardization that can be applied to all the instruments: infact there are ProFile 29 reamers and ProFile 29 Hedstroem etc.

1.j C+Files

·         The C+Files (www.dentsply-maillefer.com) are files devised to facilitate the location of the canal orifices and the initial exploration of calcified canals.

·         Available in ISO diameters 8, 10 and 15 with lengths of 18, 21 and 25 mm, the C+Files show a characteristic resistance to deformation, derived from the robust quadrangular cross-section, which allows the operator to exert 143% more pressure during insertion into a canal than would deform a K-File of corresponding size.

·         The C+Files have depth gauge black markings along their shaft, which indicate 18, 19, 20, 22 and 24 mm from the tip, aiding the positioning of the silicone stop and allowing an accurate check of the insertion depth of the instrument.

·         Ultimately the pyramidal tip of the C+Files favours the penetration in calcified canals, while their metallic surface has been subjected to an electropolishing process, which makes them particularly smooth, thereby reducing the friction against the canal walls and the accumulation of debris in the spaces between the blades.

1.i Ergoflex

·         The Ergoflex K-Files (www.fkg.ch) are files obtained by microgrinding that are characterized by a particular flexibility, depending on the depth of the blades, by the blunted tips for security and an ergonomic handle that prevents undesired intra-canal rotation of the instruments.

·         Available in steel and nickel titanium with ISO diameters from 8 to 70 and lengths 21 and 25 mm, the Ergoflex K-Files are particularly efficient in cutting by filing but must not be rotated in the canal as they do not have a high torsional strength

1.l Triple-Flex

·         The Triple-Flex file (www.kerrdental.com) is obtained by twisting a steel wire with a triangular crosssection, has a cutting tip and is characterized by high flexibility, torsional strength and debris removal capability.

·         The Triple-Flex file is available in ISO diameters from 08 to 80 and lengths of 21, 25 and 30 mm

1.m Ultrasonic Files

·         The ultrasonic files (www.satelec.com) are practically K-Files without handles, which can be mounted using appropriate inserts on the ultrasonic handpiece.

·         They are available for various ultrasonic units namely Satelec, Spartan and EMS.

·         Until a few years ago they were recommended for root canal shaping, currently they are used to passively activate the irrigating solution before canal obturation.

·         The use of the ultrasonic files for canal shaping is not recommended due to their tendency to make ledges in the canal walls and their structural fragility.

1.n Senseus Files

·         The SenseusTM, (www.dentsply-maillefer.com) are instruments in stainless steel characterized by a large and ergonomic silicone handle that gives the operator an increased tactile feedback and increased working comfort .

·         The Senseus line consists of 4 instrument categories FlexoFiles, FlexoReamers, Hedstroem and ProFinders.

·         All the Senseus have calibration rings along the shank which are radiographically visible and very useful for checking every level of canal penetration of the instruments.

·         The Senseus Profinders are instruments obtained by torsion of a steel wire with quadrangular cross-section

·         They are for initial canal negotiation and have a decreasing taper of the blade from the tip (where it is about .02) to the shank (where it is about .01).

·         The decreasing taper of the Senseus ProFinder and their bevelled tip of 65° favours the negotiation of narrow and calcified canals without, however, reducing the deformation strength even when subjected to relatively high pressure or torsion.

·         The Senseus ProFinder are available in three ISO diameters (0.10 mm, 0.13 mm and 0.17 mm) and with lengths of 21 and 25 mm.

·         The Senseus FlexoFiles, with the exception of the grip, have the same characteristics as the Standard FlexoFiles and like these are obtained by torsion of a steel wire with a triangular cross-section.

·         They have a bevelled Batt type tip of 55° and are available in 3 lengths (21, 25 and 31 mm) and with ISO diameters from 06 to 140.

·         The Senseus FlexoReamers have the same characteristics as the Standard FlexoReamers, just like these they are obtained by torsion of a triangular steel wire, they have a bevelled Batt type tip of 55° and are available in three lengths, (21, 25 and 31 mm) and with ISO diameters from 06 to 140.

·         The Senseus Hedstroem have blades that are identical to the corresponding Maillefer Hedstroem Files with a round cross-section obtained by microgrinding and a cutting tip angle at 65°. Like the Standard Hedstroem Files, the Senseus Hedstroem are available in three lengths (21, 25 and 31 mm) and have ISO diameters from 06 to 140.