Richard Mounce, DDS
This song title by the Doors is an apropos phrase for achieving patency through a blockage in the apical third. The foundation of quality endodontic treatment rests on the accurate determination of the true working length, correct diagnosis, canal preparation, and biomechanical cleansing of the root canal system. Along with these critical principles lies the attainment of apical patency.
Apical patency refers to the ability to pass a short No. 6-10 K file through the apical foramen at all times during treatment. Inadequate irrigation combined with improper instrument sequences increases the risk of patency loss by packing pulp, dentinal shavings, and other canal contents (dentin mud) into the apical third. This "mud" can be very difficult to bypass. If a dentist inadvertently creates a blockage and fails to remove it, ledges and apical perforations are the unhappy result.
I've outlined some strategies below to combat this problem; these solutions also are applicable when you are negotiating calcified canals. I also will discuss the effect of apical blockage on the efficiency and profitability of endodontics.
• Copious irrigation is essential. There can never be too much irrigation, but there certainly can be too little. Ideally, irrigation should be performed after every file insertion. A good option for irrigation is an EDTA gel mixed with sodium hypochlorite, 5.25 percent.
• Use an Endo Bender plier (SybronEndo, Orange, CA) to create a small J curve at the end of a 6-10 K file, depending on canal size.
• It may take 15 to 30 minutes or more to break through some blockages in a single canal. Be patient.
• Use gentle pressure, and direct the curve of the file in the same direction as the canal curvature.
• Work the file into the area of the canal that feels "spongy." It often is necessary to reinsert the J bend of the file into the canal multiple times and in numerous orientations to find the part of the canal that has some "give."
• If you can feel the file making progress, irrigate frequently and keep working this spot until you break through the blockage.
• Once you break through, use short amplitude (1 mm vertically) strokes (100 minimum) before you pull the file out of the canal. Irrigate and then repeat these small strokes until the file spins freely beyond the blockage and patency has been obtained.
• Use as many K files as needed (it will take an average of six to 10 packs in a difficult blockage). Change files often because even minimal use can dull a file quickly. It is not necessary to use flexible K files in this process. The stiffer the file, the better. Never force the file. Use gentle apical pressure. Pushing too hard may create a ledge if one is not already present.
Endodontic profitability is a hot topic in dental journals, especially for general dentists. From my perspective, achieving patency and building on that during treatment is a dramatic step toward greater profitability, as is choosing the best possible rotary nickel titanium file system with regard to cutting efficiency and fracture resistance (in my hands the K3 system, (SybronEndo, Orange, CA) and careful case selection.
And finally, there are those who believe in filing and filling short of the radiographic apex, and who do not seek patency so as to restrict the movement of instruments and filling materials out the apical foramen. A small textbook could be written on this subject, but suffice it to say, in the authors opinion, this philosophy leaves pulp in the apical third and runs counter to the objective of root canal treatment, which is the three dimensional cleansing and shaping and obturation of the root canal system from the orifice to the minor constriction of the apical foramen.
Best of luck as you "break on through to the other side" to attain patency. Excellent clinical results lie beyond.
Dr. Richard Mounce is in private endodontic practice in Portland, Ore. He lectures worldwide and has published numerous articles in the Journal of Endodontics. Dr. Mounce also writes "Endo Made Easy," a bimonthly tips feature for Dentistry magazine, and a quarterly column for Endodontic Practice in the UK. Contact Dr. Mounce via email at linek [email protected]. Visit his Web site at www.mounceendo.com.
