ROEN0210

28 I I opinion _ GTX rotary system _Nearly fourteen years ago, Dr L. Stephen Buchanan introduced the concept of greater tapered canal shaping and the GT ProFile rotary endodontic system to the world of endodontics. The GT brand is one of the most successful endodontic products in history and has a loyal following amongst clinicians around the world. The original GT ProFile rotary sys- tem (DENTSPLY Tulsa Dental Specialties) was also the first NiTi instrument to be part of a comprehensive system-based approach to endodontic treatment. For the first time, pre- dictable and consistent canal shapes could be achie- ved, followed by a size- matched obturation system, and finally a size-matched post- placement system. The system-based approachoftheGT system is brilliant because the paper points, gutta-per- cha cones, obtura- tors and posts all fit the canal shape pro- duced by the GT rotary instruments. Dr Buchanan andDENTSPLYrecentlyadvanced the proven GT ProFile system with the introductionoftheGTXrotarysystem.Belowis atechnicalreviewofthedesignfeaturesandbenefits of the new GTX rotary system. _DesiredfeaturesinaNiTirotaryinstrument In order to appreciate the attributes of the GTX system,wemustunderstandwhatisdesiredinaNiTi rotary system. Resistance to breakage, preventing canal transportation, conserving coronal dentine, creating good apical taper, and efficient cutting are what I look for in a rotary instrument system. Until now, clinicians had to choose between safe, flexible,radiallandedinstrumentsandfastercutting non-radiallandedinstruments.GTXdesignfeatures, such as variable radial land width, 1 mm maximum flutediameters,safe-endedtipconfiguration,open- spiralledflutegeometryandM-Wire,haveproduced an endodontic instrument that is both safe and efficient. _Variable radial land width Radial landed cutting edges are the only blade designproventomaintaintheoriginalcanalpathand thereforepreventcanaltransportation.Figures1and 2 illustrate the difference between a radial landed cuttingedgeandanon-radiallandedcuttingedge.In Figure 1, the radial land portion is the portion of the filethattrailsthecuttingedgeandcontactstheradial arc. It is the trailing radial surface that limits lateral cutting forces in a curved canal and prevents canal transportation. Figure 2 shows a non-radial landed triangular cross-section with only the apices of the triangle contacting the radial arc. The non-radial landed cut- tingbladedesigninFigure2ismorelikelytotransport a curved canal. Similar to the original GT system, the new GTX instruments have radial landed cutting edges. Newer manufacturing technology has allowed for the radial land width to change over the length of theinstrument.Thevariableradiallandwidthfeature of GTX allows for thinner radial lands and enhanced cuttingefficiencyinareaswherecanaltransportation is less likely. Wider width radial lands are used in areas in which canal transportation is more likely to occur. The outcome is improved cutting efficiency without compromising safety. Along with radial landed cutting edges, GTX has the same rounded tip designastheoriginalGTfiles.Thisfeatureiscriticalto preventing ledge formation and transportation. _Maximum flute diameter The 1mm maximum flute diameter is the best feature of the original GT system and has been retainedinthenewGTXinstruments.Maximumflute diameter is defined as the largest diameter of the in- strumentfluting.Itoccursatthemostcoronalaspect of the instrument’s taper. A conventional tapered in- strument has a continuous taper for 16mm and the maximum flute diameter is different for different in- strumentsizes.Forexample,aconventionalsize30tip 0.06 tapered instrument has a maximum flute diam- eter of 1.26mm, which is a diameter 26% larger than that of a 30 tip 0.06 tapered GTX instrument. All in- struments in the GTX system have a maximum flute diameter of 1mm regardless of the tip size or taper. Fig. 1_File cross-sectional view showing a radial landed cutting edge design—the radial land is the portion of the file that trails the cutting edge and contacts the radial arc. roots2_2010 The GTX rotary system Author_ Dr Chris J. Lampert, USA Fig. 1