Page 14 - The Beauty and Sorrow in Endodontics (WL and C/S)

safe to do so. The same extra care must be taken when a file is used to “peek out” the

apex (Fig A7). The action of gentle sliding a small file (eg. ISO #10) out the RT to
maintain patency of the canal is called “peeking through” (Fig A8).

D. Envelope of Motion (EOM): Simultaneous rotation and translation

1. The root canal is an enveloped system surrounded by dentinal walls, and any

instrument used is limited to within this narrow and closed space. Utilizing the
EOM is critical to successfully enlarge and shape the canals.

2. Multiple random points of contact between the canal wall and the file creates a

smooth curvature that shapes the canal.

3. During root development, aside from the disturbance from existing structures that
can result in curvature of the root, uneven secondary and/or reparative dentin

formation along the canal wall can also result in irregular canal shape. This
requires the use of EOM to smoothen the canal walls (Fig A9).

4. The operator is performing the same motion during EOM, but the resultant contact

points between the file and the canal wall is random and different each time and
thus will slowly enlarge the canal following the original canal shape through the

advancement of files.

E. Recapitulation

Recapitulation is the sequential re-entry and re-use of previously employed
instruments within the root canal. It permits gradual smoothing and tapering of the

preparation at all levels, and frees instruments coronally for controlled shaping
apically. A set of three files (eg. ISO #15, 20, 25) is re-entered in the canal multiple

times utilizing the EOM to gradually smooth the canal walls until the proposed final

apical taper is reached.

F. Flow: let the canal take the file, instead of the file making the canal

The key concept of EOM is to allow the canal to passively take in the file and not

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