Removing separated files with the Terauchi File Retrieval Kit

This blew my mind because, for me, any practice day that includes the occurrence of “Short File Syndrome” is a really bad day in the life of most any dentist who provides RCT services to patients. I skeptically asked him how he could say that with a straight face, and he told me that it only takes him one to five minutes to remove most any separated file from a root canal.

So now I have heard two different and apparently ridiculous statements from Yoshi; first, that he does not fear file breakage, and secondly, that he considers the retrieval of broken files to be a predictable procedure requiring relatively little time to accomplish. REALLY? Fortunately, knowing Yoshi for years allowed me to suspend disbelief about these outrageous statements long enough to query him for an explanation. And what he told me turned all of what I supposedly “knew” about file retrieval on its head.

These popular myths included:

• Ultrasonic tips should trough the outside-of-the-curvature canal wall.
• Ultrasonic tips work best dry when attempting file retrieval.
• File segments that have been loosened with ultrasonic vibration are nearly removed.
• Retrieving broken file segments necessitates weakening of the tooth.
• Files segments cannot be removed from the apical third of a curved canal.

Here are the critical truths about removing separated files, most of them discovered by Yoshi, and the Terauchi File Retrieval Kit (TFRK) he has designed to accomplish this previously challenging procedure (Fig. 1).

Troughing the canal wall on the inside of the curve

Perhaps the greatest paradigm shift in my thinking on this subject circled around where we should work ultrasonic tips next to the fractured surface of the file segment. It seems logical to trough the canal wall on the outside of its curvature, because that is where the fractured edge is engaged. The counter-intuitive truth, as explained to me by Yoshi, is that troughing on the outside of the canal curve doesn’t work because: a) troughing that wall increases the curvature of the canal, while cutting the inside-of-the-curve canal wall straightens the canal, and b) activating the ultrasonic tip on the outside-of-the-curve wall hammers the file segment and actually moves it farther into the canal. When Yoshi first explained this to me, I got the dumb chills. Troughing on this side of a canal requires his small ultrasonic tip ends to be bent, without kinking, so they can slide down the inside of the curve, but what a difference it makes to do it this way.

Yoshi has designed two beautiful Micro-Spoon Tips (Fig. 2) that he uses to cut a trough between the file and the inside of the curve. The two Micro-Spoon Tips in the TFRK face toward (the 6 o’clock tip) and away from (the 12 o’clock tip) the ultrasonic handpiece and are chosen relative to the direction of the canal curvature and the position the handpiece will be in while the tip is used to cut a trough on the inside canal curvature, adjacent to the file segment.

All the ultrasonic tips in the TFRK are made of ductile stainless steel and they are extremely elongate, making them easy to pre-bend but susceptible to premature breakage if not used correctly. The appropriate power setting for use of these tips is typically in the lower quarter of the ultrasonic unit’s power range and must be activated intermittently by tapping the foot control rather than in continuous mode. Intermittent switching keeps the tips from overheating and sends a relatively powerful ripple through the long, thin instruments. After two or three pulses, the tips are removed and examined for derangement, they are cooled and cleaned with a wet alcohol 2-by-2 sponge, and are then replaced for further work until the file is loosened. Working ultrasonic tips next to file segments with continuous use rather than pulsed activation also increases the risk of breaking the file segment into smaller pieces.

Cutting dry but ejecting file segments wet

Dentists typically use ultrasonic tips without water spray so that the tip can be seen as it works, and this is how the TFRK tips should be used until the file segment has been loosened. However, once the file segment has been loosened, it can be quite difficult to get it to come out of the canal unless 17 percent EDTA solution is added to the canal and a TFRK Spear tip (Fig. 3) is used in a push-pull manner, again, between the file segment and the inside-of-the-curve canal wall.

The Spear Tips are extremely thin and sharp at their tip ends — a necessity for them to further vibrate file segments, yet allow space for the file segment to escape between the Spear Tip and the canal diameter at the level of separation. While they are manufactured to a fine point, it is recommended by Yoshi that the latch-grip rubber polishing point included in the TFRK be used to further thin and sharpen the Spear Tips before and between uses as they will dull with use, rendering them too large at their ends to allow the file to escape when vibrated.

Having never considered removal of a file segment with fluid in the canal, I am still amazed at the difference this makes to the outcome. Most of the time the file segment simply disappears from the canal, having shot out at high speed, sometimes landing on the rubber dam outside the tooth.

File length as a predictor of retrieval

The third critical issue influencing file retrieval that Yoshi has figured out is that the length of the file segment is actually more important than its position in the canal. He has determined, through experimentation done in extracted teeth and proven in patient’s teeth, that the length of the broken file segment influences the difficulty of its removal; that file segments greater in length than 4.3 mm will often require more than Micro-Spoons and Spear-shaped ultrasonic tips to eject them from the canal.

Early in the development of his technique, after Yoshi realized the importance of file segment length, he would intentionally break separated files longer than 4.3 mm by using higher power settings and more continuous activation of an ultrasonic tip. Unfortunately, this caused more frequent breakage of ultrasonic tips and required another trough to be cut farther into the canal to loosen and remove the remaining, most apical portion of the separated file after the more coronal segment had been removed.

It was the search of a better solution to this conundrum that inspired him to invent what I call the Yoshi Loop (Figs. 4-6), a stainless steel micro-lasso that extends from the end of a stainless steel cannula attached to a handle with a retraction button for tightening the Loop around a loosened file segment. Like the ultrasonic tips, the Yoshi Loop is small, fragile, and easily broken when misused, but a larger tool will never retrieve a file segment from a canal.

Also, it must be carefully prepared before attempting to encircle a previously loosened file segment. The red retraction button is moved forward to extend the wire lasso, a DG-16 explorer tip is placed inside the lasso, and the retraction button is then carefully pulled backward until the loop is felt to tighten on the explorer tine, thus rounding the loop so that it may be placed around the end of the file segment. Before removing the explorer from the Loop, it is rotated back to near parallel to the cannula to bend the rounded Loop to a 45-degree angle. This rounded, angled Loop wire is then ideally formed to drop around the end of the file segment as it is moved into position (Figs. 7a-d).

Once the Loop wire is felt to tighten around the file segment, it is carefully tugged in several directions until the file is pulled out of the canal (Fig. 8). If, as often happens, the wire lasso slips off the file segment, it is simply removed from the canal, reformed, placed back over the file segment and tightened once again.

Developing adequate coronal canal shape without weakening the root

When file segments are below the orifice level, a staging preparation to the broken file end is usually required and is accomplished with the TFRK Modified #3 Gates Glidden bur (Fig. 8) at 1000 RPM clockwise, then the TFRK Micro-Trephine bur (Fig. 9) at 600 RPM rotating in a counter-clockwise direction, so as to encourage a bound file segment to reverse thread back coronally and loosen. If the file segment is around a curve in the canal, the TFRK includes a 70-.12 GT Accessory File to create a better, more straight-line visual access to the file segment. All three of these instruments have tip diameters of 0.7mm, a very safe size to cut a staging preparation through coronal root structure to the separated file segment.

Removal of file segments beyond the middle third of the canal

This is where my experience level is still developing, and I usually refer clinicians to Yoshi’s Facebook page for review of his cases or advice about their own cases, and as such I will leave this to our own god of file retrieval. There are several YouTube videos of his simple and more difficult cases, and I find them an excellent review before tackling my next challenge in the art of file retrieval — a skill that I never expected to master at the level he has brought me so far.

In my own experience, understanding Yoshi’s concepts of file retrieval made it possible to remove broken files — mine and other’s — that I would have never expected to be possible. Using the tiny, elegant tools in the Terauchi File Retrieval Kit have made it a wonderfully predictable procedure to have in my bag of endodontic tricks.

For further information about the TFRK, visit Dental Education Laboratories at delendo.com and DentalCadre — the provider of Terauchi’s TRFK — at dentalcadre.com.