Written by Richard Mounce, DDS Monday, 31 March 2003 19:00
Most of us at one time or another have pulled a rotary nickel titanium (RNT) file out of a canal to find that the file is a little shorter than it was before insertion, prompting the sinking feeling known as the “heartache of separation.” At present, there are an ever larger number of RNT instrumentation systems available in the marketplace. Fracture of RNT files is the single greatest problem with their use despite the dramatic improvement they represent in enhanced shaping of root canal systems.
TEN STEPS TO PREVENTING INSTRUMENT SEPARATION
The following suggestions should help prevent the heartache of RNT instrument separation (Figures 1 through 7): (1) Do be gentle and deliberate in your motions with these files. Never put more force on a RNT file than you would use on a soft lead pencil.
|Figure 1. The “Heartache of Separation.” A rotary nickel titanium file was inappropriately placed into a canal at 1,500 rpm and full torque, and fractured mid root.|
|Figure 2. File removed microsurgically and the canal obturated. Prognosis is excellent.||Figure 3. Fracture of this rotary nickel titanium file occurred because the operator took the file to the end of the root without establishing a proper glide path.|
|Figure 4. Canal obturation after microsurgical removal of the separated instrument and re-treatment of the other 2 canals.||Figure 5. Multiple files separated in the same tooth. Removal is complicated by the horizontal component of the files’ existing position that is not evident radiographically.|
|Figure 6. File removal complete prior to obturation.|
|Figure 7. Case completed; although not aesthetic, prognosis is excellent.||Figure 8. Using a tapered rotary nickel titanium instrument first, such as the 0.06 K3 files (SybronEndo), from the larger tips sizes to the smaller incorporates crown down instrumentation as each successively smaller file progresses farther down the canal passively.|
(10) Do use an electric motor to power the files. Air-driven gear reduction handpieces tend to have variable torque and rotational speeds that predispose the RNT to fracture in certain canals. Following the torque settings, manufacturer’s instructions, and automatic presets on some electric models are key for effective use of the files. Do not rely on a warning signal sound or auto reverse to know when to discontinue use of a file. Some files are designed to be used at high rpms and full torque only in the coronal third of a canal, and if used apically can fracture very quickly, especially if the operator is waiting for a warning sound, which the machine may not be programmed to deliver.
Following the simple steps above can go a long way toward eliminating the “heartache” and providing the joy of more predictable and profitable endodontics. Both we and our patients will appreciate it.
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