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roots - international magazine of endodontology

I 35 new product technique _ shaping canals I roots1_2015 tatingNiTifilesaremany,allcommerciallyavailable file systems are influenced by cyclic fatigue and torque, especially in longer, narrower and more curved canals. Cyclic fatigue, caused by the structural alteration and work hardening of the metal, is induced by re- peated tensile–compressive stress, especially when preparingcanalsexhibitingcurvature.7 Torsionalfail- ure caused by using too much apical force occurs more frequently than flexural fatigue.8 Specifically, taper lock results when an excessive length of a file’s active portion binds in the canal during rotation. Un- desirabletaperlockpromotestorsionalfailureandfile breakage. When the canal diameter is narrower than thediameteroftherotatingfile,thelatterhaslimited ability to progress deeper into the canal, binds and then potentially unwinds and/or breaks.9 _From rotary to reciprocation While the majority of commercially available NiTi systems are mechanically driven in continuous rota- tion, reciprocation—defined as any repetitive up and down or forward and reverse movement—has been used to drive endodontic instruments since 1958. Early attempts at reciprocation utilised alternating, butequal,forwardandreverseanglesofeither90de- greesor,morerecently,smalleranglesof30degrees. As such none of these instruments ever complete a full rotation. Although these reciprocating systems offer an alternative to manual preparation, multiple- filesequences,apicaltransportation,reducedcutting efficiency, inward pressure and limited debris re- moval remain issues.5,10 However, with a novel recip- rocating movement of unequal bidirectional angles that complete a full forward rotation of 360 degrees after four 90-degree cutting cycles of reciprocation, just one single file can start and fully complete the preparation of a canal to a perfect shape.11 A single- filetechniqueinconjunctionwithanovelreciprocat- ingmovementhasbeenclearlyshowntoreduceboth cyclic fatigue and torsional failure, preventing broken instruments.12 In2008,theconceptofthe“single-filetechnique” was adopted by DENTSPLY International as a project in collaboration with eight international clinicians to produce a more optimal, dedicated, safe, unique reciprocating single file and to identify the most suitable unequal bidirectional angles with a motor system to generate this movement. The outcome was the launch of RECIPROC (VDW) in 2010 and WaveOne(DentsplyMaillefer)in2011.Bothsystems were marketed as simple, efficient and predictable automated methods to shape canals and embraced by many general dental practitioners looking to move intoautomated canal shapingafteryearsofunsuc- cessful attempts with manual techniques and val- ued both in terms of time and cost savings. Fig. 3a_WaveOne GOLD tip and profile. Fig. 3b_WaveOne GOLD ogival tip design. Fig. 4_The WaveOne GOLD file engages 150 degrees CCW and 30 degrees CW, turning 360 degrees after three cycles of reciprocation. Fig. 4 Fig. 3a Fig. 3b

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