Many root canals can be done in one appointment, although it is dependent on the particular situation. After removing the nerve and blood supply, or dead tissue, from the canals; and cleaning and drying the canals, the canal must stay dry in order to get a predictable seal when filling the canal. If the canal still has puss or other fluids backing up into the canals, a common treatment would be to place calcium hydroxide in the canals, wait a week or two and then do the final canal fill at the second appointment. The calcium hydroxide does not allow the infection start up again in the canal during that time. Thanks for the question, Dr. Belongea.
Chad M. Belongea