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.
Are you ready for the Pacific Dental Conference 2018 next week?
Come and join me for an overview of the “shaping” and “cleaning” stages of root canal treatment.
Sometimes when the conventional endodontic access is not possible, the unconventional approach can save the day.
A clinician should always aim at establishing a straight line access (SLA) in order to properly instrument, irrigate and obturate the canal system. Depending on the initial challenges, establishing a SLA could mean accessing an anterior tooth through its buccal surface [example below], accessing an anterior tooth through its incisal edge, or accessing a molar tooth through its mesial marginal ridge or its MB cusp.
When I went through my undergraduate dental training, I was taught that MB2 canals in upper molars are there 60-70% of the time. Newer tools and techniques show us that MB2’s are always there whether or not we can get to it. As a matter of fact I tell our endodontic residents at UBC that “if you haven’t found it, you have missed it“.
Here are some pointers on how and where to find the canal that can potentially result in endodontic failure if left untreated, specially if the tooth is necrotic to begin with:
“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.
Some of you may wonder how a long root with moderate to severe curvature should be instrumented. Some clinicians may also be hesitant to use rotary instruments in such roots and therefore resort to using handfiles.
Here are some pearls that I learned during my training:
1. The first step in staying out of trouble is to scrutinize the x-ray really well before starting the treatment. I find myself guilty of not doing what I preach sometimes and I realize mid-treatment how severe the curvature was or the fact that the canal was not completely instrumented with the rotary files to length at the end of treatment (i.e. the second case presented above shows sealer in the last 2mm of this long canal).
2. We only see curvature in 2-D. Canals are almost always curved in bucco-lingual direction as well (i.e. usually MB canals of upper and lower molars have a buccal curvature in the cervical 1/3 , the ML canals of the lower molars are curved buccally in the middle or apical 1/3, the DB canals of upper molars and D canals of lower molars are curved buccally and distally to mention a few).
3. The shaping stage of root canal treatment should be done in 1/3‘s: coronal 1/3, middle 1/3, apical 1/3. I always start by preparing access cavity, locating canals, scouting the coronal 1/3 with sizes 8 and 10 SS files, coronal shaping with rotaries, redefining the access (to achieve straight line access), working length determination with EAL (trust the apex locator more than the x-ray if it is reading well), middle and apical shaping.
4. Why do I not bother establishing the actual working length until the straight line access and coronal shaping are completed? Calcification always starts coronal to apical. If you are careful with the instrumentation of the cervical 1/3, you will never lose or block the canal (be patient when negotiating tight canals!). If you see the canals in the middle and apical 1/3 of the root pre-operatively but your files are struggling, you are dealing with narrow canals, deep splits or curvatures. Go back to your last file and by using filing motion make enough room for the next one. Use lots of irrigation.
5. Follow steps 3 and 4. Use a set of fresh rotary files. In teeth with long curvy roots, use smaller tapered instruments (0.04 or 0.02 tapers).
And remember: “Chance favors only the prepared mind. –Louis Pasteur”