Cleaning the Lateral Canals
SOMETIMES root canal treatments fail. One reason for failure is incomplete cleaning of the lateral (accessory) canals. Roots have fins and webbings between canals. These are often difficult to discover and difficult to access. So how do you clean these inconspicuous areas? Instrumenting these tiny channels physically is difficult, so you have to rely on cleaning them chemically with endodontic irrigants, such as 5.25 percent sodium hypochlorite, 17 percent ethylenediamine tetraacetic acid (EDTA), 2 percent chlorhexidine, or MTAD.
During instrumentation, a smear layer is produced on the canal walls. This consists of dentinal debris, pulp tissue (vital or necrotic), odontoblastic processes, and sometimes bacteria. Because the smear layer may be infected, trapping bacteria in the dentinal tubules, I think it is best to remove the smear layer, especially in necrotic cases. Also, the smear layer may act as a physical barrier, interfering with adhesion and penetration of sealers into dentinal tubules and lateral canals. EDTA is a chelating agent that effectively removes the smear layer, opens the dentinal tubules, and produces a clean surface for a better endodontic fill. EDTA does not have any antibacterial activity, so it is effective when used with 5.25 percent sodium hypochlorite. I like to use 2 percent chlorhexidine as a final rinse.
MTAD is another irrigant that came out almost ten years ago. It consists of tetracycline isomer, an acid, and a detergent. MTAD has the ability to remove the smear layer and also has antimicrobial ability. It is recommended to be used with a diluted 1.3 percent sodium hypochlorite solution.
By removing the smear layer with EDTA or MTAD, better penetration into the lateral canals may be achieved, as shown in Figures 1 and 2.
July - September 2012