How can I prevent getting blocked out of a canal during root canal instrumentation?
Once the canal orifice is identified, a precurved size 10 stainless steel file is gently twisted back and forth while it is advanced slowly and with light pressure to the apical third of the root canal. An irrigant such as sodium hypochlorite should be used during this instrumentation.
When the file reaches the apical third region, it can be operated in short amplitude movements in and out of the canal rather than in back-and-forth (stem-winding) movements. This is especially important in tight, calcified canals when the file is slowly advancing apically, because the strength of a stainless steel hand file operated in a push–pull motion is greater than the torsional strain that is exerted when winding a file back and forth.
A lubricant such as an ethylenediaminetetra-acetic acid (EDTA) preparation may be chosen at this point to replace the sodium hypochlorite irrigant. The size 10 file can be moved in a filing motion 20, 30 or even 40 times to create a smooth canal pathway, then replaced with a precurved size 15 file. Once the size 15 file reaches the apical third region, it can be moved in a back-and-forth filing motion to create a smooth pathway from the canal orifice to the apical region, in a manner similar to the size 10 file.
At this stage, it is advantageous to perform coronal flaring of the coronal and middle thirds of the root canal system. This is typically done using some form of crown-down technique, beginning with larger instruments at the coronal end of the root canal and changing to progressively smaller diameter instruments to advance further apically. Coronal flaring of the root canal system allows for deeper penetration of canal irrigants and lubricants, and provides a better tactile sense of hand instrumentation in the apical third.
Dr. Jeffrey Coil is an assistant professor in the division of endodontics, department of oral biological and medical sciences, faculty of dentistry, University of British Columbia, Vancouver, British Columbia. He is the president of the Canadian Academy