Page 26 - The Beauty and Sorrow in Endodontics (WL and C/S)

Shaping Facilitates Cleaning

One should not expect to disinfect the canals through simple debridement or
enlargement of the canal space only, it is impractical and nearly impossible to do.
Instruments are marketed to dentists every day that aim to make treatments simpler and
easier for the operator. Operators relying on NiTi rotaries that claim to shape the canals in

as short as 2-3 minutes often end up over-shaping the canal walls, weakening the roots
and putting them at risk of fractures in the future (Fig B1, B2). Furthermore, if regular
irrigation is not done, the constant motion of the rotary file against the walls will result in

a smear layer that blocks the lateral canals and shields the pathogens inside against the
disinfectants. On the other hand, operators who don’t shape the canals properly, either
due to their fear of file separation or perforation, etc, often leave pathogens in the
complex apical anemic deep shape that can flare up in the future (Fig B3, B4, B5).
Anemic deep shape results in limited irrigant efficacy and cone fit prematurities.

Overshaping results in weakened structure or strip perforations.

Important Concepts of Cleaning and Shaping

1. The files are used to shape the irregular dentin wall into a smooth tapered canal that
mimics the natural flow of the roots;
2. Ensure sufficient quantity and contact time (and if possible, ultrasonic activation) of
the irrigants in the canals and chamber for proper disinfection;
3. There is no need for the file to touch every single point on the canal wall;

4. Do not remove important dentinal wall structure unless necessary;
5. It is important to properly shape the apical thirds of the canal to allow for penetration
of the irrigants and ideal placement of the master GP cone;

6. There is no magical obturation technique that can densely fill the complex apical
system, including accessary and lateral canals, without proper shaping of the canals.

Always Clean the Apical Last
The main cavity of a root canal can be divided into three segments: coronal, middle, and

apical thirds. Traditionally, the idea was to determine the working length as soon as
possible (See “Working Length”). If the operator is lucky enough to get the small file
right down to the radiographic terminus, then cleaning and shaping of that particular

canal would be a piece of cake. However, most root canals are irregularly shaped, and it
is very difficult and risky to force the file down. Therefore, the crown-down concept was

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