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”