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Endo Tribune Middle East & Africa Edition No. 6, 2016

Dental Tribune Middle East & Africa Edition | 6/2016 endo tribune A2 Twisted-FilesAdaptive: ANovelApproachtoEndodonticNiTiInstrumentation ByDr.AdiMoran,UK A major goal of Endodontics is the prevention or elimination of “apical periodontitis”. Apical periodontitis is the general term for endodontic related periradicular/periapical in- flammation, whether it is histologi- cally a granuloma, cyst or abscess, in symptomatic or asymptomatic form.1 When root canal treatment is indicated, we rely on the triad of in- strumentation, irrigation and obtu- rationtoachievethisgoal. Instrumentation has come a long way since we first started using NiTi alloy in root canal preparation. Ini- tially research concentrated mostly on features of file design such as ta- per, cross section, blade rake angle, pitch, tip design and so on. We then went on to improving the metal- lurgical properties of NiTi alloys for even more enhanced flexibility and fracture resistance. More recently we started also researching kinemat- ics of NiTi files in root canals in the searchofoptimisedpreparation. Today we know a lot about advan- tages and disadvantages of features from all these three categories through the vastly accumulated evi- dence based research. ‘TF-Adaptive’, as a motor and file system, was bril- liantly designed with a focus on providing the clinician with a huge set beneficial features at hand while greatlyreducingthepotentiallimita- tions. During canal preparation the systemshiftsautomaticallybetween file rotation motion and reciproca- tion, each when most desired and appropriate. This in turn results in an ability to safely prepare root canals – file separation almost worry free – not only quicker then before but also re- spectingtheoriginalcanaltrajectory, improving circumferential canal preparation and greatly minimising debris extrusion compared to other reciprocatingsystems.32 Rotationvs.reciprocation From the 90s,“traditional” NiTi root canal instrumentation has been done through continuous instru- ment rotation. More recently, Yared introduced the concept of canal in- strumentation using a single NiTi file using reciprocation movement.2 Since then, reciprocation has been the focus of much research and des- ignated motors and NiTi files have beenbroughttomarket.Thebenefits of reciprocation helped in making thesefilesystemsquitepopular. In time, independent research has shed more light on these advantag- es but also on disadvantages when comparing root canal preparation by reciprocation with the traditional continuous rotation. We now know that when considering some impor- tant aspects, continuous rotation remains superior to reciprocation, while the opposite is true when con- sidering other aspects.9,13-16 TF Adap- tive is the only system to smartly empowertheclinicianwithbothfea- tures in one single program mode. It does this by a sophisticated auto- matic torque algorism that uses ro- tation when we want it and recipro- cation when we need it. The system does this skillfully, eliminating the needforclinicianstoswitchbetween theprogrammesettingsontheendo motorduringcanalshaping. In a reciprocating movement the file rotates in one direction, engag- ing and cutting the dentin, and then rotates back to a lesser degree, disen- gagingfromthedentin.Thisextends the cyclic fatigue resistance on the file, reducing stress on the instru- ment to a degree where it is possible topreparetheentirerootcanalusing a single NiTi file.12,17,11,23,25 This is usu- ally not possible when using NiTi filesinacontinuousrotationmotion andservesasastrongsellingpointto preparation by reciprocation vs. by rotation. The other major advantage of recip- rocating movement is the ability to better preserve original canal trajec- tory (Fig 1.).16,26 This is attributed to overall lower instrumentation stress applied on canal walls. However, other factors need consideration too and rigid files or ones with cut- ting tip designs would (negatively) greatly affect and promote transpor- tation, even when a file reciprocates. It can also be argued that preparing canals with a single NiTi file is sim- pler and to some degree might be quicker.18,19,20 On the other hand preparation by pure reciprocation is known to in- crease the incidence of post-opera- tive pain, brushing laterally may be less efficient, less emphasis is given to the straight line coronal access (pre-flaring) phase of preparation and also apical enlargement is not alwaysaddressedbyasingleNiTifile. 1. Increased incidence of post-op- erative pain is due to significantly greater debris pushed out as a con- sequence of the file movement in a full reciprocating mode.9,32 This is true for vital cases and even more so when, in non vital cases, the debris being pushed out is infected.22 On the other hand, in pure rotation, file flutes are designed to push debris upwards away from the apex, result- ing in significantly less debris push- out.21,19 2. After shaping to entire canal length and reaching the master api- cal file, we want to brush laterally to achieve as much main canal circum- ferential cleanliness as possible in an asymmetric oval canal where our instrument is round and centered. Rotation with ultra flexible files (such as Twisted Files) with effective cutting blades does this job more efficiently than with a reciprocating motion.4,29,30 This is achieved beauti- fully using the TF Adaptive System in the “TFA Program Mode”. Given the width of the canal at this stage, the file works in rotation only with low torque applied on it. The same could be achieved also by switching to the pure “Twisted File Full Rota- tion Mode” at a push of a button on themotor. 3. Single file endodontics is not al- ways advised, especially when treat- ing molar teeth where different canals of the same tooth may vary greatly in dimensions. For example, asinglereciprocatingfilesize25with taper .08 might be sufficient when preparing MB1 and DB canals of an upper first molar tooth. Yet in most cases this file size would not be as compatible for MB2 canals, and cer- tainly not compatible for the P canal of the same tooth. In such cases, if a single reciprocating file is used, we may need to resort at a later stage to thestepbackorotherrigidfilestech- niques for apical enlargement. This is still far less beneficial than simply usingseveralhighlyflexibleNiTifiles of various taper and apical dimen- sions to tailor our needs and combat eachcanalmorespecifically,without compromise. The TF Adaptive Sys- tem lets us decide during each case whether to complete the work using a single NiTi file or to adapt with one or two more files. The “bigger” files (yellow and then red) are designed with enlarged apical size but with re- duced taper. They therefore remain highly flexible despite being bigger in size.10 This feature is important when the canal is highly curved but at the same time a greater size apical enlargement is required. This is eas- ily and safely done with the apically wider yellow and red TFA files after thesmallergreenone(ML1)tookcare of the taper in the coronal two thirds ofthecanal. 4. Lastly, there is the misconception about pure reciprocating systems being truly single NiTi endodontics, where in reality it is recommended to firstly produce a glide path wide enough to require up to three more files,whichmaybeNiTiones.33,34 R-Phasetechnology NiTi alloys are super elastic (highly flexible) and have shape memory (return to original shape after flex- ing) due to a reversible atomic crys- tal lattice shift between the Austen- ite and deformed Martensite states. This atomic shift happens when externaltensionisappliedonthefile bytherootcanal.24 However, the ability to create this atomic shift also depends on ambi- ent temperature and on the alloy’s thermal pre-treatment during the manufacturing of the endodontic file. Manufacturing with specific thermal pre-treatment, (know as R-Phase), further contributes to the abilityoftheNiTifiletoabsorbstress and resist fatigue resulting in greatly enhancedfileflexibilitycomparedto NiTi’smanufacturedwithtraditional techniques. Twisted Files are manu- facturedbytwistingtherawmaterial to shape during a thermal cycle that transformsintotheR-Phase.7 As mentioned above, the reversible atomic confirmation also depends on ambient temperature. It is inter- esting to note that at room tempera- ture, the atomic file confirmation is in the stable Austenite phase. We need to actually reduce the tem- perature in order to shift into the Martensite phase. Manufacturing under R-Phase gives the file proper- tieswhichallowustocoolafilechair- side with a conventional endo cold spray to a temperature range where the NiTi file stays bent long enough for us to precurve the file, like we do with stainless steel ones (Fig. 2 and 3).8,25 This is greatly beneficial when managing ledged root canal cases (Fig.4). Until this technology came along, the conventional approach for ledge management required extra work and chair-time using one pre-curved stainlesssteelfilesaftertheother.27 Without doing this first the normal NiTi file would go naturally into and stopattheledgepoint.Evenmoreso, the very severe ledges could not be “cancelled” well enough with stain- less steel. These cases required the continuation of canal preparation to master apical file without being able touseNiTifilesatall. Having cooled the TF Adaptive File with a cold spray, we pre-bend the file, quickly insert it with a tactile hand motion beyond the ledge, then connect it to the headpiece and choose to either first brush laterally in an anti-curvature up/down mo- tion trying to cancel the ledge as much as possible, or continue with gentledownpeckingapicallyinstead. It is also important to note that ca- nals with problematic ledges which were effectively prepped to length with NiTi files are easier to obturate with the continuous wave of obtura- tion warm technique, as opposed to those prepped with stainless steel alone. Innovativefiledesign28 Twisted Files are the only files in the market manufactured in the same way as stainless steel ones, by twist- ing them into shape. This is done during the thermal cycle that trans- formsintotheR-Phase. •Theresultisasmoothandcontinu- ousfilesurface.AllotherNiTifilesare groundedintoshape.Themachining process leads to machining grooves on the surface of the file. File frac- turealwaysstartsattheweakestlink. These machining surface grooves serve as initiation points for cracks andthenpossiblyfilefracture.31 • In addition to twisting, Twisted Files then further undergo a process ofsurfacedeoxidationforevenmore enhancedsurfacesmoothness.5,6 • The Twisted Files’ cross section is a triangular one. This results in effec- tivedentincuttingallowingustouse the same file both as a reamer and then later as a Hedstrom file to effec- tivelybrushlaterally. • The Twisted Files’ pitch configura- tion varies along the file rather than being constant. This reduces the “pull-in” effect and creates smooth tracking during root canal prepara- tion. •TheTwistedFiles’tipisasafeended non cutting pilot. The tip guides and does not dig. This helps in reducing occurrencesofcanaltransportations. TheTFAdaptiveway Operator use feels ‘different’ com- pared to pure rotating modes, yet the overall learning curve is quick andyougettolovetheentiresystem verysoon. The system is designed to shift auto- matically between interrupted rota- tion to start with and reciprocation. The rotation reaches 600 degrees then stops and restarts to a new 600 degrees loop. This gives the benefits of rotation, i.e better cutting and de- bris being pushed upwards. With in- creased load further down the canal and beyond the curves, the system will then gradually shift to varying reciprocation angles, as required. This is different to the traditional reciprocation systems with constant clockwise/counter clockwise angles. Under higher torque stress, TF Adap- tive rotates 370 degrees clockwise and up to 50 degrees counterclock- wise. This provides further safety against file separation and canal tra- jectory is highly respected (Fig. 5 and 6).10,32 TheML(MediumLarge)fileset is a true crown-down technique. The taper of the first file facilitates better irrigation while the next ones work moreonapicalenlargement.TheSM (Small)setmanagesscleroticcases. Clinicaltips Following access cavity preparation, achieving straight line access is an Fig.1.Highdegreecurvatureinapical thirdofdistalroot canal. Fig. 4. Referred case with ledge in apical thirdofmesialcanal Fig. 5. 1 year review. Ledge was managed withpre-bent SM2.Healingapicaltissues. Fig. 6. Double curvature management with reduced risk to file separation in the secondcurve. Fig.2.TFA-SM1 Fig.3.TFA-SM1kept at apre-bent statewithhelpofcoldspray. ÿPageA3

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