Root canal procedures present numerous challenges due to the porous nature of the root structure and ease of penetration of microbes inside that porous structure once the tooth is dead and deprived of blood supply. Currently it is impossible to completely clean the entire canal system of a tooth. If a dead tooth is infected, it can only be attempted to reduce infection as much as possible within the limitations of present treatment modalities. (Ref: Riskwise # 7 - NZDA Newsletter vol. 127, Nov. 2005. ) This is further confirmed by a 2006 study published in the International Endodontic Journal.

Once the canal or canals in a root have been cleaned as best as possible, the canals have to be filled. Usually the canals are filled with a combination of gutta percha, a rubbery material, and a sealer designed to insure a seal between the internal walls of the canal and the gutta percha. Many commonly used root canal sealers have been proven to be toxic as can be seen by reading the results of the studies on sealer toxicity.