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28 I I clinical technique _ WaveOne _The new WaveOne NiTi file system from DENTSPLY Maillefer is a SINGLE-use, SINGLE-file system to shape the root canal completely from start to finish. Shaping the root canal to a continuously tapering funnel shape not only fulfils the biological requirements for adequate irrigation to rid the root- canalsystemofallbacteria,bacterialby-productsand pulp tissue,1 but also provides the perfect shape for 3-D obturation with gutta-percha.2,3 In most cases, the technique only requires one handfilefollowedbyonesingleWaveOnefiletoshape the canal completely. The specially designed NiTi files work in a similar but reverse “balanced force” action4 using a pre-programmed motor to move the files in a back and forth “reciprocal motion”. The files are manufactured using M-Wire technology, improving strength and resistance to cyclic fatigue by up to nearly four times in comparison with other brands of rotary NiTi files.5 Therearemanydentistswho,forwhateverreason, arereluctanttouseNiTirotaryinstrumentstoprepare canals,despitetherecognisedadvantagesofflexibil- ity, less debris extrusion and maintaining canal shape, amongst other advantages.6–8 For them, the use of a single reciprocating filewillbeveryattractivebothintermsof time and cost saving. At present, there are three files in the WaveOne single-file reciprocating system available in lengths of 21, 25 and 31mm (Fig. 1): 1. TheWaveOneSmallfileisusedinfinecanals.Thetip size is ISO 21 with a continuous taper of 6%. 2. The WaveOne Primary file is used in the majority of canals. The tip size is ISO 25 with an apical taper of 8% that reduces towards the coronal end. 3. The WaveOne Large file is used in large canals. ThetipsizeisISO40withanapicaltaperof8%that reduces towards the coronal end. The instruments are designed to work with a reverse cutting action. All instruments have a modi- fied convex triangular cross-section at the tip end Fig. 1_WaveOne Small (yellow), Primary (red) and Large (black) files. Fig. 2_WaveOne apical cross- section, modified convex triangular. Fig. 3_WaveOne coronal cross- section, convex triangular. roots1_2011 The WaveOne single-file reciprocating system Authors_DrJulianWebber,UK;DrsPierreMachtou&WilhelmPertot,France;DrsSergioKuttler,CliffordRuddle&JohnWest,USA Fig. 2 Fig. 3 Fig. 1