Name two methods for managing severely curved or constricted canals.

• A. Crown-down or step-back preparation with flexible NiTi instruments
• B. Use of rigid stainless steel files only
• C. Immediate obturation without glide path
• D. Irrigate with undiluted saline only

Answer: (A)

When canals are severely curved or constricted, the aim is to maintain the original path of the canal while effectively cleaning and shaping it. Flexible nickel-titanium instruments are crucial here because they follow curves better than rigid stainless steel files, reducing the risk of transportation, ledges, or perforation. Two effective approaches with these flexible tools are crown-down preparation and step-back preparation.

Crown-down shaping starts by enlarging the coronal portion first, creating a straight-line access that improves irrigation flow and reduces resistance as you work apically. This minimizes force on the apical region and helps the file reach the apex without binding. Step-back preparation complements this by shaping the apical portion to the appropriate size first and then progressively enlarging the more coronally, creating a taper that preserves canal integrity while facilitating obturation. Together, these methods minimize iatrogenic errors and adapt to the canal’s curves.

Choices that rely on rigid files, omit a glide path and proper cleaning, or use irrigation alone without effective disinfection do not address the challenges of curved or constricted canals.