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Endo Tribune United Kingdom Edition

The exploration file (#10 MMC) serves to evaluate the root canal’s complexity. It is introduced into the root canal without axial con- straintsinthecoronalzone,owing to the previous action of ENDO- FLARE. Any coronal interference that might hinder the file’s pas- sage must be eliminated to make the treatment as safe as possible (Fig.6). Thesecondstepoftherootcanal preparation is the exploration of the root canal and the creation ofaglidepath.Thisstepentailsthe pre-enlargement of the root canal and facilitates the passage of the following rotary shaping instru- ment. Root canal exploration and glide path development are per- formed with stainless-steel hand files or rotary NiTi files.8 It has been shown that the use of a highlyflexibleinstrumentwithan asymmetrical cross-section re- duces the risk of canal transpor- tation.9 In addition, this kind of cross-section combined with a variable helical pitch diminishes screwing effects.11 The second rotary instrument intheOneShapeProcedurePackis OneG(Fig.7).ThisNiTiinstrument with a diameter of 0.14 and a 0.03 taper has an asymmetrical cross-section. Its three cutting edges are situated on three differ- ent radiuses to the root canal axis. One G also has a variable helical pitch and thus variable helical angles. The narrower the angle, the more active the rotating in- strument,andthewidertheangle, the greater the efficiency of the instrument’straction.8 Allofthese featuresprovideOneGwithahigh flexibility and great efficiency. Clinically, if the root canal is patent, One G is taken to the work- ing length (WL) previously deter- mined with the #10 MMC file and anapexlocator.However,iftheroot canalisnotpatent,OneGpenetrates with vertical up-and-down move- mentsonthecanalaxisdowntothe length attained by the #10 MMC file. This allows the elimination of constraints in the cervical and middlethirdsoftherootcanal.The #10 file is then pre-curved in order to check the canal patency. The WL is determined and transferred to One G, which is then taken to the WL at a speed of 250–400 rpm and a maximum torque of 1.2 Ncm (Figs.8&9).Afterthecreationofthe glidepathwithOneG,the#15MMC filemustpenetratedowntotheWL withoutconstraints.Therootcanal is now ready for shaping. The third rotary instrument is One Shape (Fig. 10). This NiTi instrument with a diameter of 0.25anda0.06taperhasavariable cross-section. The apical 2 mm of itsactivebladewithagloballength of 16 mm has a triple-helix cross- section with three cutting edges situated on three different ra- diuses to the canal axis. The fol- lowing 7.5 mm constitutes a tran- sitional zone that terminates in a double-helix section of 6.5 mm in the coronal part of the file.12 Thecuttingeffectofthetwocut- ting angles in the coronal zone is more important and allows more efficienteliminationofthedebris, whereas the three cutting angles in the apical zone provide the instrument with a better centring ability, a higher resistance totor- sional constraints and a better capacity to negotiate curves.13 The instrument’s tip is inactive and allows for a smooth progression in the root canal. The helical pitch and angle are variable along the instrument and thus guarantee better upward transport of the debris and limit screwing effects. Owing to its characteristics, One Shape causes less extrusion of de- bris and irrigating solution in the apical zone than other single-file systems available on the market.14 Theinstrumentprogresseswith an up-and-down movement of low amplitude and without exces- sivepressure.OneShapeisusedin continuous rotation with a speed of 350–450 rpm and a maximum torque of 2.5 Ncm. Root canal shaping is performed in three steps with progression of One Shape to two-thirds of the WL, 3 mm short of the WL, and the WL (Fig. 11). Between each passage, the root canal is abundantly irri- gated with sodium hypochlorite and patency is checked with a #10 file. The instrument’s spires must be systematically cleaned and visually inspected. One Shape performs the root canal preparation quicker than other single-file system.15 This gain in time must be used for the indispensable final irrigation. Editorial note: A list of references is available from the publisher. 23Endo Tribune United Kingdom Edition | 6+7/2015 TRENDS&APPLICATIONS DrTaraMcMahon is a working as a dentist in an endodonticprac- tice in Brussels, Belgium. PRINT DIGITAL EDUCATION EVENTS The DTI publishing group is composed of the world’s leading dental trade publishers that reach more than 650,000 dentists in more than 90 countries. AD Stress-free, relaxed working: Since the instruments are single-use only, the risk of instrument fracture due to cyclic fatigue is considerably re- duced and there is no risk of cross- contamination. Short learning curve: All of the rotary instruments are used in continuous rotation. Rapidity of the root canal preparation: The gain in time during root canal shaping allows for a more thorough final irrigation. Simplification of the operating proce- dure: A single instrument is used for glide path creation, and one instru- ment for root canal shaping. Gain in time for the dental assistant: Simpler and quicker preparation of the working materials, since no cleaning and no sterilization of the instruments are required after the treatment. Thus, there is more time to assist the practitioner during treatment. Optimised organisation in the dental office: Stock management is easier and less storage space is required. 17b 17d Figs.17a–e: Pre-op photograph (a).Radio- graphofOneGinthesecondmesiobuccal canal (b).Radiograph of One Shape in the secondmesiobuccalcanal(c).Radiograph with the master cone (d). Post-op radio- graph (e).” 17c17a 17e

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