If you are interested in an endodontic refresher lecture, come and join me next Thursday at the Pacific Dental Conference (PDC 2019). Two and a half hours lecture filled with pictures and videos demonstrating the initial endodontic treatment.
“A dentist who has not separated a tip of a file, reamer, or broach has not done enough root canals.” — Louis Grossman
There are essentially 2 reasons for rotary rotary instrument separation inside a canal:
1) Cyclic fatigue (file rotating inside a curved canal for extended period of time):
Factors contributing to cyclic fatigue are: overuse of rotary NiTi files, spending too much time inside the canal during instrumentation, canal curvature (degree and abruptness of the curvature), improper speed setting for the handpiece and the file tapers (larger tapers break faster).
2) Torsional fatigue (too much friction between the rotary file and the canal wall):
Factors contributing to torsional fatigue are: improper endodontic access, using too much apical pressure during instumentation, not following the proper sequence for a particular file system, not using lubricating agent/irrigants, using greater tapered files inside a tight/calcified canal and using handpieces with no torque control or auto reverse option.
Attempting to control the factors above will greatly minimize the risk of file separation. But even in a perfect situation, a patient’s canal anatomy can bring the man-made technology to its knees.
What to do if a file breaks inside a canal?
1. Stay calm. It is not the end of the world.
2. Try to remove it only if the separated portion is in the coronal segment of the tooth and not past the root curvature. This step also requires good magnification, illumination and proper tools (such as different ultrasonic tips).
3. Bypass it if the separated segment is apical to the curvature of the root using hand-instruments and finish the shaping of that canal with hand-files. Sometimes the separated file comes loose and can be easily flushed out.
4. Make it part of the filling if the file has completely blocked the canal. This may not affect the prognosis negatively [Crump and Natkin 1970, Spili et al. 2005] depending on the initial status of the pulp and whether or nor the separation happened towards the beginning or the end of cleaning and shaping stage.
5. Follow up the healing and the resolution of symptoms. Endodontic surgery may be needed if symptoms persist or the PA lesion does not heal.
“After about ten years of first appearing on the market, currently Thermafil obturators are completely modified and form an integral part of a complete and sophisticated system of root canal obturation that, when used correctly, can give optimal results. — W. Ben Johnson”
The reported advantages of Thermafil include: shortness of learning curve, speed of clinical application, apical control of fill, conservative enlargement of root canal (when compared to other warm gutta percha compaction techniques), three-dimensional obturation and apical sealing ability, etc.
In my opinion, shorter treatments do not allow for adequate disinfection of the canal system, speed compromises the quality, apical control of fill is nonexistent with this technique, and conservative enlargement of root canal is not always beneficial since some degree of apical enlargement is necessary to allow for proper disinfection by irrigants.
If used correctly (proper size obturator in a single, adequately-instrumented canal and following the manufacturer’s recommendations), 3-D obturation and apical sealing ability are the major advantages of this obturation technique.
Inappropriate case selection for the use of Thermafil obturation technique is demonstrated above. This case shows how Thermafil would give us a false sense of achieving an “optimal” obturation in challenging cases such as this. There was only one obturator used in the canal system that splits into three apically.
As I mentioned in my previous post I Love Sealer Puffs!, extrusion of obturation material into the uncleaned and unshaped portion of the canal system (lateral canals, fins, isthmus, irregular areas, etc.) does not translate into success. The prerequisite for any obturation technique is adequate shaping and cleaning of the entire system, and the only reason for endodontic failure is the presence of micro-organisms.
“Pure lateral or vertical compaction rarely occurs. The vectors of force applied during obturation techniques are an integrated blend of forces and result in composite of forces that are neither true vertical or lateral.” [Pathwyas of the Pulp-7th Ed.]
So, I guess we all pretty much use the same combined obturation technique. Downward force of finger-/hand-spreaders or pluggers and the resultant force moving the obturation material laterally. Some of you have asked me for a demonstration of my obturation technique:
After complete shaping and cleaning, I fit a sealer-coated master cone to 0.5-1mm short of the apex. I then use a heat source (Calamus Dual) and a series of 2-3 pluggers (S-Kondensers) to perform the down pack. Finally, I use the Calamus Dual again to back-fill to the level of canal orifice.
Many clinicians are interested in techniques that produce sealer puffs and show off apical ramifications. Here is a brief summary of an article that I had read a couple of years ago and it pretty much explains my stand on this issue:
“Chemomechanical preparation partially removes necrotic tissue from the entrance of lateral canals or apical ramifications, whereas the adjacent tissue remaines inflamed, sometimes infected, and associated with periradicular disease. Vital tissue in lateral canals or apical ramifications is not removed by preparation. In cases in which lateral canals appears radiographically ‘‘filled,” they are actually not obturated, and the remaining tissue in the ramification is inflamed and enmeshed with the filling material… The belief that lateral canals must be injected with filling material to enhance treatment outcome is not supported by literature.” [J Endod 2010;36:1–15]
So, clinician’s skill or the technical ability of producing sealer puffs will not necessarily result in successful endodontic therapy. In many cases, extrusion of sealer into lateral canals and ramifications as a result of specific techniques (use of patency files, removal of smear layer, use of warm vertical compaction technique, etc.) is unavoidable, but this should not be the aim in obturation.