Many clinicians are interested in techniques that produce sealer puffs and show off apical ramifications. Here is a brief summary of an article that I had read a couple of years ago and it pretty much explains my stand on this issue:
“Chemomechanical preparation partially removes necrotic tissue from the entrance of lateral canals or apical ramifications, whereas the adjacent tissue remains inflamed, sometimes infected, and associated with periradicular disease. Vital tissue in lateral canals or apical ramifications is not removed by preparation. In cases in which lateral canals appears radiographically ‘‘filled,” they are actually not obturated, and the remaining tissue in the ramification is inflamed and enmeshed with the filling material… The belief that lateral canals must be injected with filling material to enhance treatment outcome is not supported by literature.”
So, clinician’s skill or the technical ability of producing sealer puffs will not necessarily result in successful endodontic therapy. In many cases, extrusion of sealer into lateral canals and ramifications as a result of specific techniques (use of patency files, removal of smear layer, use of warm vertical compaction technique, etc.) is unavoidable, but this should not be the aim in obturation.
Dr. Donald Yu, an endodontist in Edmonton, and instructor at Boston University, would teach his students to leave 2.5% sodium hypochlorite in the cleaned and shaped canals until a separate obturation appointment, in order to eliminate all live or necrotic tissue and microbes in all the ramifications of the canals.
I am not convinced how much does leaving NaOCl inside the canal system really do. NaOCl is not known to have any residual effect when left inside a tooth. The volume that is left inside the canal system is so little that it will lose its effect very fast probably. That’s why it needs to be constantly replenished during irrigation stage of root canal treatment. Plus, if it continues to be effective while left inside the canals, who would want a very caustic material in their tooth that can easily scape into the periapical tissue and cause inflammation and destruction. I am not sure if I have read any studies on how long the tissue-dissolving and antibacterial activity of NaOCl would last if it is not replenished.
I totally agree leaving NaOCl inside the canal for the next appointment will not provide any beneficial effect.
NaOCl kills the microbes in the canal in a matter of seconds and looses its efficacy very quickly.
Sodium hypochlorite is more effective in a consentration 5.5%, low consentration has little or invaluable effect if left for several days inside canals, in addition to its undesirable effect in adhesives bonding used for post cementation.