by Richard Mounce, DDS
My recent column on warm carrier-based obturation brought a strong and personal response in a subsequent letter to the editor that appeared in the April issue of Dental Economics®. I admire passion in endodontics, even in disagreement. It is important that people express their views openly and respectfully. Suffice it to say, I recently retreated my wife’s warm carrier-based obturation and when my daughter needed a root canal, I used bonded obturation for both in the form of RealSeal (SybronEndo, Orange, Calif.). As a full-time practicing endodontist in the trenches who earns his living by treating patients (often in endodontic retreatment), a warm carrier-based obturation in its present form would not be my first choice for my family or patients for the reasons stated in my earlier column.
This introduction is a natural lead-in to a brief discussion of the removal of warm carrier-based products when required and the application of these principles to all forms of endodontic retreatment. While endodontic retreatment is not usually within the scope of general dental practice, there are crossover techniques related to one essential retreatment skill that has application in first-time orthograde treatment, i.e., regaining lost patency.
What to remember when using hand K files
In using hand K files, ideally, several important principles are observed.
Pre-curve the hand files with an instrument like the EndoBender pliers (SybronEndo). The curve is a small, gentle arc about 3 to 4 mm from the file tip.
The pre-curved hand file is placed into the canal in the expected direction of the curvature of the root. Matching the curvature of the file to the curvature of the canal facilitates its insertion.
Advancement of small hand files (Nos. 6 to 8) is slow, gentle, passive, and done initially to negotiate and “scout” the progressively deep levels of the canal. If difficulty is encountered upon advancement of the files, the curvature on the file is redirected so as to find a path where the file can advance apically but never with force. At all times the file tip is advanced bearing in mind the true working length to minimize extrusion of irrigants and debris from a patent canal. In some canals and curvatures, it can take numerous insertions to find the canal path or bypass a blockage.
With regard to warm carrier-based retreatment, silver cone retreatment, and bypassing of ledges, the aforementioned principles apply. In many such cases, there often comes a point in which bypassing the obstruction (carrier or SC) with hand files becomes essential to facilitate its removal (assuming that ideal coronal access to the SC or carrier has been obtained - either with ultrasonics, RNT orifice openers, or by hand).
Bypassing is often a time-consuming operation. Ideally, it requires a surgical operating microscope, such as the Global SOM (Global Surgical, St. Louis, Mo.) to visually tell the clinician where the best path of file insertion might be. In these clinical cases, the precurved file tip is placed into the canal and reentered, until in the presence of solvents and/or irrigants, the file tip can bypass the level of previous obstruction. Once the level of obstruction is bypassed, it is important to not immediately remove the hand file but rather use the file in short amplitude vertical strokes of 1 to 2 mm which can create a pathway alongside the carrier or SC. Slowly and subsequently, this pathway can be enlarged with the next larger hand file. In this process, it has value to potentially snip a hand file at its end to create a shorter file that is stiffer and gives greater tactile control.
Once the above steps are taken and a pathway has been created alongside the SC and/or carrier, once a number 15 hand file can be placed alongside the obstruction to reach the estimated working length, a Hedstrom file can often be inserted in the pathway. This will allow an upward rasping force to be placed on the obstruction and facilitate its removal.
In bypassing ledges, once the precurved hand file is able to pass, it is left in place with the same recommended short amplitude strokes. In this manner, the ledge will slowly be rubbed out. Particularly with apical ledges, RNT files are contraindicated since they might accentuate the ledging, lead to instrument separation, perforation, or other iatrogenic events.
As always, I welcome your feedback.
Dr. Mounce has no commercial interest in any of the products mentioned in this article.
Dr. Richard Mounce lectures globally and is widely published. He is in private practice in endodontics in Vancouver, Wash. Among other appointments, he is the endodontic consultant for the Belau National Hospital Dental Clinic in the Republic of Palau, Korror, Palau (Micronesia). He can be reached at firstname.lastname@example.org.