Endo Tribune United Kingdom Edition

June 2014United Kingdom Edition12 Endo Tribune page 11DTß curve the file in their fingers with- out an EndoBender. h) Canals should always be ne- gotiated with hand files prior to using RNT files. Even if the clini- cian uses a RNT glide path crea- tor (PathFile, DENTSPLY Tulsa or PreShapers, SpecializedEndo), the canal should be first negotiated by hand to assure patency. Clini- cian preference dictates whether a glide path should be created by hand files or RNT files. i) In the view of the author, hand files are single use disposable in- struments as they dull rapidly dur- ing clinical function. j) The use of nickel titanium hand files is a matter of personal prefer- ence.Whilesomecliniciansdesire the flexibility and shape memory of nickel titanium hand files, oth- ers do not. It should be noted that nickel titanium hand files are available with controlled memory, a proprietary thermo mechanical process in which nickel titanium hand files lose their shape memo- ry yet retain their flexibility.2–4 k) The principles of canal prepa- ration must be observed, irre- spective of the methods utilised to achieve these principles (ie hand file canal enlargement and/ or RNT enlargement or a combi- nation of these methods). These principles are to: • leave the canal in its original position (simply enlarge it as described here) • leave the minor constriction (MC) of the apical foramen at its original position and size • create a tapering funnel with narrowing cross-sectional di- ameters from orifice to apex • create a master apical taper that optimises irrigation and obturation hydraulics, and yet causes no iatrogenic events (strip perforation, canal transportation unnecessary dentin removal—and does not leave the tooth at risk of long term vertical fracture) General classes of hand files Files primarily designed for ca- nal negotiation In calcified canals, hand file stiff- ness is an attribute. Mani D Find- er files are representative of this class and are especially useful for early negotiation of calcified canals. The D finders have a D shaped cross-section. Some files utilise carbon steel in manufac- ture and/or possess atypical tip sizes to facilitate negotiation. Stiff- ness can be attributed to either the files design (Mani D Finders) or the use of carbon steel and/or a combination of carbon steel and a modified design (Pathfinder CS, Axis/SybronEndo) (Fig. 1). K files Generally, K files have a three or four-sided configuration with more spirals than a K reamer. Mani K Files are four-sided. Over- all, K files are the most “universal” hand files covering the greatest number of clinical indications. K files are not as flexible as hand files designed specifically for flex- ibility (such as the Mani Flexile files discussed below) or nickel titanium hand files. K files are used with a watch-winding hand motion and can be reciprocated (as described below). The angle between the cutting flutes and long axis of a K file is generally in the 25-40o range.5 Lexicon K Files are an additional example of another commercially available K file (DENTSPLY Tulsa). K Reamers Mani K Reamers are three-sided and contain fewer spirals than K files. Smaller reamers are gener- allysquareincrosssection.Larger reamer sizes are generally trian- gular. The angle between the cut- tingflutesandlongaxisofareamer is most often in the 10-30o range.5 Reamers are used in rotation, unlike K files. Hand file rotation is associatedwithlesscanaltranspor- tation than K file watch winding. The use of K reamers versus K files is a matter of personal prefer- ence. K type instruments of both types (reamers versus K files) should be manipulated carefully when used counter clockwise due to the risk of instrument fracture. Lexicon K Reamers are an addi- tional example of a commercially available K reamer (DENTSPLY Tulsa)—these are triangular in cross section. H files H files (Mani H Files as well) have conical spirals ground into them. They are used on the pull stroke for gross removal of canal con- tents in the coronal third and in retreatment. H files should not be rotated due to fracture risk inher- ent in their design. The angle be- tween the cutting flutes and long axis of an H file is generally in the 60-65o range.5 It is not advisable to use H files near the MC. The MC can be transported easily if H files are used at or beyond the MC. Clini- cally, aside from transportation, such an action lead to significant apical bleeding (Fig. 2). Hand files of accentuated and variable taper Mani Flare Files are more tapered than standard hand files—0.05 ta- per compared to 0.02 taper. They are used to prepare tapered ca- nals for doctors who hand file the entire preparation among other more specialised uses such as verifying taper before cone fit. Accentuated taper is also available with nickel titanium GT Hand Files. ProFile 0.04 Hand Files are 0.04 tapered and come in a variety of tip sizes, again in nickel titanium. ProTaper Univer- sal Hand Files feature the ProTa- per variable taper design in shap- ing and finishing files in various lengths (all of the above are man- ufactured by DENTSPLY Tulsa). Flexible Files Mani Flexible Files are triangu- lar in cross section. Files with a triangular cross section are more flexible than those with square cross sections. Flexible stainless steel hand files are generally used in easily negotiated canals. Clini- cian preference dictates whether to use flexible stainless steel files relative to nickel titanium hand instruments (Fig. 3). Additional files in this class are Lexicon FlexSSK Files (DENT- SPLY Tulsa). These files are also available in medium sizes (12, 17, 22, etc.). Aggressive cutting files Mani RT files (possessing a paral- lelogram cross-section) and a 71o cutting angle, making them more aggressive relative to many of the other files included here. RT files would be used primarily by doc- tors who are hand filing the entire canal in conjunction with other hand files (Fig. 4). Nickel titanium files GT Hand Files (made of nickel titanium) are available in various tapers and tip sizes (DENTSPLY Tulsa). Lexicon FlexNTK Files are made of nickel titanium and come in various tip sizes while maintaining a constant taper. As mentioned above, clinician pref- erence dictates whether a flex- ible stainless steel file is more desirable than a nickel titanium hand file. Medium sizes, K, H and reamers Mani provides K Files, H Files and stainless-steel reamers in me- dium sizes (12, 17, 22, 27, etc.). ProFile Series 29 Stainless Steel 0.02 Hand Files have a constant 29 per cent increase in tip size in 0.02 taper. Use of medium sizes avoids the dramatic increase in tip diameter with increasing tip sizes, especially between a #10 and #15 hand file (a 50 per cent increase in size of the #15 relative to the #10 hand file). Safe-ended hand files and recip- rocation Mani SEC O files are available in an H and K file variety. Both are “safe-ended,” as they do not cut on their tips. The Mani SEC O K File is ideal for reciprocation. SEC O H files (and H files in general) are not reciprocated (Figs. 5 & 6). Reciprocation is a very safe technique, whereby the clinician can uses a reciprocating hand piece attachment to replicate manual hand file watch wind- ing. Clinically, reciprocation is used after the canal has been ne- gotiated to the TWL and recip- rocation proceeds with the first file that binds at TWL. In this ar- ticle, the terms TWL and MC are synonymous. The purpose of re- ciprocation is to save time, re- duce hand fatigue and prepare a space into which RNT files can subsequently be inserted with minimal torque stresses (prepare a glide path). Reciprocation is inherently safe. It is difficult to fracture hand files when this technique is used appropriately. Fracture or iatro- genic misadventure generally occurs when the files are inappro- priately placed (well beyond the MC), the wrong type of hand file is reciprocated (H) and/or the speed is grossly exaggerated above the recommended levels. Reciprocating hand piece at- tachments fit onto an E-type coupling and can be powered at 900rpm, for example at the 18:1 setting on an electric endodontic motor. To initiate reciprocation, the file is left in the canal at the TWL and the reciprocating hand piece is placed over the file (the file is inserted into the head of the re- ciprocating hand piece and is held there while reciprocating). The attachment reciprocates the file clockwise and counter clock- wise— for example, with a 30-de- gree clockwise and 30o counter clockwise movement. These at- tachments do not rotate the file a full 360o — in contrast to how 12

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