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ePaper created 2016-09-05, 09:33:59 | version 1.38.0
canal shaping technique | 17 roots 3 2016 techniques.29, 30 However, recent studies have shown that commercially available reciprocating instru- mentation techniques seem to significantly increase the amount of debris extruded beyond the apex31, 32 and, consequently, the risk of postoperative pain. A clinical study comparing Reciproc and NiTi rotary instruments has also confirmed these findings.33 Sincereciprocationmovementisformedbyawider cuttingangleandasmallerreleasingangle,whilero- tating in the releasing angle, the flutes will not re- move debris but push them apically. Reciproc and WaveOne motions are very similar (even if not pre- ciselydisclosedbymanufacturers),andthisfactcould also explain the higher incidence and intensity of postoperative pain that has been found in recent re- search studies.33, 34 Moreover,bothWaveOneandReciproctechniques use a quite rigid, large single-file of increased taper (usually 08 taper, size 25), which is directed to reach the apex. In many cases, in order to reach the apical working length, reciprocating instruments are used with apically directed pressure, which produces an effective piston to propel debris through a patent apical foramen, and possibly directing debris later- ally, making canal debridement more difficult. Since instruments are commonly used without first per- forming preliminary coronal enlargement, this may result in a greater engagement of the file flutes and consequently may produce more torque and/or ap- plied pressure on the file. Moreover, the cutting abil- ity of a reciprocating file is decreased when com- pared to continuous rotation. Debris removal is also less, thus increasing the frictional stress and torque demand on the file, due to entrapment of debris within the flutes. To reduce this tendency some au- thorshaveadvocatedtheuseofNiTirotaryglidepath instruments, before using a WaveOne or Reciproc in- struments,butinthiscasetheoveralltechniqueisno longerasinglefiletechniquebutamorecomplexand more costly technique which utilises two different typesofNitiinstruments,glidepathinstrumentsand then shapers.35, 15 TF Adaptive TheTFAdaptivetechniquehasbeenproposedinor- dertomaximisetheadvantagesofreciprocation,while minimisingitsdisadvantages.Byusingaunique,pat- ented motion, the innovative TF Adaptive Motion technology,togetherwithanoriginalthree-filetech- nique, most clinical cases can be treated effectively and safely (Fig. 2). TF Adaptive employs a patented unique motion technology, which automatically adapts to instru- mentation stress, when used in the Elements Motor whileinTFAdaptivesetting(Fig.3).WhentheTFAdap- tive instrument is not (or very lightly) stressed in the canal, the movement can be described as a continu- ous rotation, allowing better cutting efficiency and removal of debris. The cross-sectional and flute de- sign are meant to perform at their best in a clockwise motion. More precisely, it is an interrupted motion with the following CW-CCW angles: 600–0°. This interrupted motionisaseffectiveascontinuousrotationinlateral cutting,allowingoptimalbrushingorcircumferential filing for better debris removal in oval canals. This interrupted motion also minimises iatrogenic errors by reducing the tendency of ‘screwing in’ (aka pull down), that is commonly seen with NiTi instruments of great taper that are used in continuous rotation. Onthecontrary,whilenegotiatingthecanal,dueto increased instrumentation stress and metal fatigue, the motion of the TF Adaptive instrument changes into a reciprocation mode, with specifically designed CW and CCW angles that may vary from 600–0° to 370–50° (Fig. 4). These angles are not constant, but vary depending on the anatomical complexities and theintracanalstressesplacedontheinstrument.This ‘adaptive’motionisthereforemeanttoreducetherisk of intracanal failure, without affecting performance, due to the fact that the best movement for each different clinical situation is automatically selected by the Adaptive motor. It is quite interesting that the clinician will hardly perceive the differences in the changing motion, due to a very sophisticated algo- rithm, which permits a smooth transition between the changing angles. As far as disadvantages of reciprocation are con- cerned, TF Adaptive motion is a reciprocating motion Fig.6: Deep shaping.The clinical use of a second instrument (06/35) after the 08/25 significantly increases the preparation in the apical one third, improving the quality of canal shaping and allowing room for enhanced irrigation.This will also allow the use of the apical negative pressure devices such as the EndoVac to safely deliver abundant quantities of sodium hypochlorite to the apex without the risk of apical extrusion. Fig.6 32016