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<p>Brent J. Crumpton, DC, USN and Captain Scott McClanahan, DC, USN<br><br>The purpose of this clinical update is to bring clinicians up to date with three current and popular endodontic rotary nickel-titanium instrument systems.<br><br>Background<br>Since the end of the nineteenth century, automated root canal instrumentation has been available, but systems had many problems. The challenges of increased canal blockage, instrument breakage, and insufficient canal debridement were related to the use of stainless steel instruments and have been dramatically improved with the introduction of nickel-titanium (NiTi) files. The first useable NiTi alloy was developed by William Buehler in 1960 at the U. S. Navy Ordinance Lab in Silver Spring, Maryland. Walia et al. investigated the feasibility of using this alloy in the fabrication of endodontic files, and showed that NiTi files had two to three times the elastic flexibility in bending and torsion, as well as superior resistance to torsional fracture when compared with stainless steel files of the same size. These features led to better centering of the instruments within the canal, less straightening of the canal, fewer elbows and ledges, and less transportation.<br><br>NiTi rotary instrumentation should always be performed with slow-speed, low-torque or “right-torque” electric motors. A variety of motors exist from varying manufacturers including the Tecnika ATR and Aseptico ITR both of which were designed specifically for endodontics and are supplied by Tulsa Densply. These types of electronic motors have preprogrammed speed and torque values preset by the manufacturer for their recommended instruments. The units also allow the operator to adjust the manufacturers’ settings to the specific needs of the user. An additional benefit to the electric motors is the auto-reverse feature which is activated prior to reaching the elastic torque limit of the file, potentially reducing the possibility of instrument separation. Also available are air driven motors that connect to a slow-speed attachment on the dental unit. The air driven motors are less expensive than the electric motors. However, they are unable to control torque and do not have an auto-reverse feature.<br><br>The past few years have seen a dramatic increase in the number of manufacturers producing NiTi rotary files. The most popular systems are marketed by Tulsa Dental and Sybron Endo (formally Analytic Technologies). Tulsa markets both the ProSystem GT and ProTaper lines of rotary instruments, where Sybron Endo markets K3 (the successor of the Quantec line of files).
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<br>Subjects: endodontics ; Root Canal Preparation ; Root Canal Therapy</div>
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U.S. Navy. Naval Postgraduate Dental School</div>
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