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26 I I opinion _ instrumentation these perceptions. From a practical point of view, the smallestapicalpreparationthatallowsforeffectiveir- rigation is a size 30, with a size 35 apical preparation stronglyrecommended.Thereareanumberofarticles thatcloselycorrelatethedegreeofapicalpreparation withreducedbacterialcount;reducedbacterialcount is closely associated with higher success rates.4,5 From the above discussion, it is evident that supe- riortactileperceptionoffersthedentistthetoolstodif- ferentiate between encountering a solid impediment andnegotiatingatightcanal.Theformersituationpro- ducesnoimmediatetug-backontheinstrument,while the latter does. No tug-back indicates that the dentist shouldremovetheinstrumentfromthecanalimmedi- ately,pre-benditatthetipandseektonegotiatearound thepresentimpedimentmanually.Thisdifferentiation is essential to avoid deviating from the correct canal path by the dentist making his/her own canal in error. The cutting tip of relieved reamers confined to a tight manual watch-winding motion or the 30° reciprocat- inghandpieceeasilynegotiatestotheconstrictionand then0.5mmbeyondtoassurepatencythroughoutthe shaping procedure, which in turn keeps the instru- mentscentred,minimisingthechancesofcanaltrans- portation.6 By instrumenting 0.5mm beyond the con- striction using a size 25, the canals can be predictably openedtotheconstrictiontoaminimumofsize35,size 401mmback,andthenoverlayedwithasize25/06ta- per without distortion, assuring a space that is suffi- ciently large to be well irrigated with NaOCl, digesting chemically any organic debris that may have been missed mechanically. Non-distortion is a result of the modifiedbalancedforcethatisgeneratedwhenatight watch-winding motion is employed. In the same way, the30°reciprocatinghandpiecemimicsthistried-and- provenmanualmotioninkeepingthetipsoftheinstru- mentswellcentredwhilenegotiatingcurvedcanals. Rotary NiTi files use a motion that can never provide new information about what is occurring at thetipoftheinstrument.WhenusingrotaryNiTi,any information on the apical anatomy of a canal is first attained by employing K-files, instruments that are designed and used in ways that—as this discussion has attempted to address—are incompatible with shaping the canals without distortion and assessing theirapicalanatomyaccurately,attimeserroneously giving the dentist the impression that the canals are narrower than they may be. Relieved reamers are used in a way that assures long life, virtually eliminating separation and giving the dentist more accurate information to determine the width to which the canals should be shaped, with the flexibility to be used both manually and in the reciprocating handpiece. Their use in this manner is supported by a growing body of research that clearly demonstrates that superior results are attainable, while reducing costs per use by 90% compared to rotary NiTi. It is thus no surprise that this alternative approach is garnering increasingly more enthusiastic attention.ClinicalexamplesareshowninFigures5to7. For more information regarding this highly effec- tive and safe approach, please contact me at my free online forum www.endomailmessageboard.com._ Editorial note: A list of references is available from the publisher. roots2_2010 DrBarryLeeMusikant EssentialDentalSystems,Inc. 89LeuningStreet S.Hackensack,NJ07606 USA E-mail:info@edsdental.com _contact roots Fig. 7Fig. 6 Fig. 5