Cleaning, Shaping and Irrigation
Cleaning, Shaping and Irrigation tests whether you can create a continuously tapered preparation while preserving anatomy and delivering irrigants to the apical third.
Core rules
- Establish a glide path, determine working length with an apex locator and radiograph, and maintain apical patency without enlarging the foramen.
- Shape with crown-down or balanced-force techniques; the goal is a smooth taper, not maximum apical size.
- Irrigate with NaOCl for antimicrobial effect and tissue dissolution, EDTA for smear-layer removal, and CHX as an alternative when NaOCl is unsuitable; avoid mixing NaOCl and CHX without an intermediate rinse.
- Irrigant delivery matters: side-vented needles, slow expression, and activation improve penetration; never wedge a needle in the apical third.
- Recapitulate and re-irrigate to prevent dentine debris packing.
Worked example
A curved mesial root accepts a size 10 file to length. After crown-down flaring, a size 20/04 rotary file reaches length with a passive glide path. A side-vented needle is placed 2 mm short of working length, NaOCl is expressed slowly, and the canal is recapitulated. This sequence cleans the apical third while reducing extrusion risk.
Traps that cost marks
Overinstrumenting the apical foramen; trusting a single working-length method; leaving smear layer and debris; using NaOCl as a lubricant rather than an irrigant; and failing to recognise that irrigation cannot reach untouched canal space.