No More Screwing Into The Tooth By: Marshall White, DMD
Official DentalTown Townie

Any dentist that performs endodontic procedures, who one day happens to browse through Kraus’ classic text Dental Anatomy and Occlusion perhaps years after their first year of dental school, may be taken as I was by the timeless B&W cross-sectional photographs of teeth contributed by David Sullivan. Scores of them: many showing that, contrary to what we’d think looking at PA’s daily, when most teeth are sectioned through a bucco-lingual plane their root canals are anything but conical. Most of us will pay lip service to the anatomic realities we knew in that first year of our training, but many of us (or maybe it’s only me…) tended to ignore that reality when it came to coursing our way to the apex of a root in the midst of endodontic therapy. And especially with the advent of quicker and easier instrumentation using rotary nickel-titanium files.

This mea culpa is not intended to portray myself in a poor light or affect humility, nor is it to pass judgment upon any colleague. It provides a striking contrast to much of my own workaday endodontic thinking and reveals a certain realization that again came over me when I first began reading about Ultradent’s new system for performing endodontic preparations. One of the main thrusts of their system is the notion that many, if not most canals, are not conical but rather are shaped in either an ovoid or flattened ribbon-like shape over most of their length. Modern rotary NiTi instrumentation tends to either lead us, or we are being taught, to use it in a manner that assumes all canals are essentially conical in shape. It struck me that nothing could be further from the truth.

Ultradent (www.ultradent.com) calls this system Endo-Eze® AET (Anatomic Endodontic Technology). Their primary objective is to remove as little healthy root structure as possible. This allows the root’s natural canal anatomy to dictate preparation shape, to the degree that it is possible. It uses six stainless-steel files for most cases (Fig. 1). All are essentially K-files: three in their new Endo-Eze Reciprocating Handpiece (Fig. 2) and three hand files. It is followed by an obturation method that uses their new resin sealer, EndoRez™ with a single cone of cold gutta percha.

Fig. 1 The pre-packaged file kit for the Endo-Eze system. Three files for bulk preparation with the handpiece (right), and three for final apical preparation by hand (left).		Fig. 2 The Endo-Eze reciprocating handpiece.

Instrumentation
Once access to the pulp chamber has been made, the canal orifices located, and straight-line access to those orifices facilitated using burs to shape the access cavity, one must now begin to call upon that anatomical knowledge once memorized in gnathology class during the first year of dental school. An approximate length is measured on a PA, and then we take that length and subtract 3-4 mm’s for our initial working length, placing a rubber stop on the #1 shaping file. Lubricant is placed in the canal orifice if possible or on the file and we take it to the initial working length by hand and work it a bit just as we would with any method of instrumentation. For confirmation, the length to the apex may be determined here as well with electronic methods. But I’d suggest forgoing it if you use a PA. We’ll do this more later in this article.

Next, set that same #1 shaping file in the Endo-Eze handpiece, stopper at the same pre-apical length. The handpiece files #1-3 are all non-end-cutting. This #1 file is narrow and thin, with a tip diameter of 0.10mm and a taper of 2.5%; it is essentially analogous to an ISO #10 file. Again with lubricant, it is gently inserted to that length, a few millimeters short of the apex, with the engine running and water spraying from the handpiece head and moved about in the canal in a manner that is in keeping with our knowledge of the likely cross-sectional shape of that canal. So, if working on a bicuspid that has a single canal, we move the file buccally and lingually and draw the file up and down as we press the file with some measure of lateral force against the narrow buccal and lingual curves of the ovoid shape within that canal, or passing it back and forth within a ribbon-shaped one. If the fit is loose, and our tactile sense reveals that the mesial and distal walls provide no resistance, we also wipe the running file against these walls a few seconds, loosening and removing debris and predentin there as well. Remove the file after a few seconds, irrigate, and place lubricant (Ultradent provides File-Eze®, an EDTA lubricant). Repeat this using the other two handpiece files: the #2 file, with 0.13mm tip diameter and 4.5% taper; then the #3 file, also with 0.13mm tip diameter, but a 6% taper. Irrigate. At this point, we have completed the initial bulk instrumentation.

The Endo-Eze handpiece is a very nice instrument. It is a 30-degree reciprocating handpiece, so it has little or no tendency to bind, and hence little or no ability to unwind, kink or separate a file. While it is easy to conjure up the old Gyromatic handpiece when trying to envision this instrument, such an analogy is much like comparing a belt-drive slow speed to today’s higher-end air-driven models. This baby is smooth. It is designed and made in Austria, and has the attributes of many Teutonic-engineered gadgets oft loved by dentists like KaVo handpieces and upscale German automobiles. The head has a push-button chuck. The chuck is deep with no latch-type cutout; the files come in 5 different lengths. And the file can be set in it to within 3-4mms of depth, so a stop is not always necessary (Figs. 3 & 4). The old Gyromatics were a 90-degree reciprocating handpiece. The ones I used rattled and rolled and were known for packing debris apically and actually flaring apices. Perhaps it is due to the way this new technique starts short of the apex, perhaps due to the superbly made mechanics of this handpiece and it’s 30-degree envelope of rotation, but used as directed I have had no problem maintaining apical patency in this technique nor have I been able to detect any ledging or transportation apically.

Fig. 3 The face of the head of the handpiece, showing the mechanism that holds files, and openings for water and chip air.		Fig. 4 A #3 bulk instrumentation file inserted in the head for use.

Ultradent refers to the mechanical effect imposed upon canal walls by the files in their reciprocating handpiece as “milling.” In addition to the advantage of not “screwing into the tooth” as is the potential effect of a fully rotary system, they maintain it allows greater control of how aggressively dentin is removed, so it is more conservative especially in inexperienced hands. I found this to be true, but must caution it can be quite aggressive (it oscillates at 5,000–6,000rpm). If you allow a file to dwell too long in a curved canal, the rigidity of the larger files coupled with this ability to cut could easily perforate an inner curve or transport an apex in the next step, so respect is a good virtue to bring along with the technique. This is not a magical fail-safe cure for a heavy hand or a too-tight schedule. Like any mechanized endodontic technique, it is powerful. To manage highly-curved canals, the technique requires an ability to properly establish straight-line access with a consistent glide path, a good reading of the manual and a couple of additional files. Yet even then, the technique is easily mastered, fast, simple and conservative.

After the initial shaping is completed as above, determine the actual final working length electronically or radiographically. Repeat use of the earlier three files #1-3 in the handpiece, this time using only a vertical movement and irrigate between files, to within about a millimeter of the apex. Final apical preparation to a #30 is straightforward and accomplished by hand using the last three files in the kit. Ultradent has additional files for use when the situation calls for great diameter apically (Fig. 5).

Once rinsed and dried, a GP point is fitted in the classic manner, so as to obtain “tug-back” if desired.

Fig. 5 A set of apical preparation hand files for use when the case demands preparation to larger diameters at the apex.		Fig. 6 The EndoRez double-barreled syringe, with auto-mix tip attached. EndoRez is dispensed directly into the rear barrel of the Skini delivery syringe for placement into a canal.

Obturation
It has long been understood that gutta percha alone against dentin leaks. Sealers (if placed adequately at that interface) diminish leakage and resin-based sealers, due to their low solubility and ability to actually adhere to dentin, may hold the greatest potential for preventing leakage in a method of endodontic obturation. Similar to a few other techniques, Ultradent has developed their own means to accomplish this with their new resin sealer and obturant, EndoRez™, using a single-cone technique. EndoRez is a methacrylate-based auto-set resin sealer that comes in a double-barreled automix syringe of its own (Fig. 6).

Key to this system of obturation is a newly-developed disposable delivery device: the Navi-Tip metal cannula or needle on a small narrow syringe, the Skini syringe. Leave it to Ultradent, masters of some of the best delivery gadgets in our arsenals, to come up with this gizmo (Figs. #7 and #8). This syringe-and-tip allows the EndoRez to be placed at the apex and the canal back-filled with it–that’s right, bottom up. The Skini syringe is just like it sounds, a very skinny syringe designed to hold a small fraction of EndoRez sealer, dispensed into it’s rear end directly from the automix tip of the EndoRez dispensing syringe. The Navi-Tip cannula is exceedingly small in diameter, blunt-ended, and is more flexible toward the end than nearer the hub to allow it to be pre-bent or curved and gain access to the apex in curved canals. Once placed to the end of the canal, the EndoRez is delivered as the Navi-Tip is slowly withdrawn. Lastly, a standard .02 taper cold GP point is placed. The canal tapers more than the .02 taper point, so excess EndoRez is expressed coronally and the point cut or burned off at the canal orifice.

Fig. 7 A “Skini” syringe with NaviTip attached and plunger below.		Fig. 8 Close-up of a 21mm NaviTip. These are 30 ga (0.31mm) blunt-ended cannulae and easily curved to reach a canal apex. They come in four lengths from 17-27mm.

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Marshall White, DMD, is a wet-gloved dentist to the common man. In 1995, after a decade of solo and associateship practice, he founded Optimal Dental Care, Ltd., focusing upon using the most conservative, long-lived and patient-friendly techniques. An avid nightly participant at www.DentalTown.com, Dr. White is a self-described “Simple Country Dentist” and a tireless advocate of scientifically-based clinical practice. An aficionado of both the written and spoken word, he resides on 5 acres of wooded bliss in rural Licking County, Ohio, with his wife Jennifer, their two young sons (with a third due in Oct. ‘02) and a veritable menagerie of dogs, cats and wild fauna. Dr. White welcomes any and all communication and may be reached at (740) 344-1200, or by email at drwhite@optimaldental.com.

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