This may lead to continued pain and discomfort in the tooth until the fourth canal is found and properly treated. The second molar can have a fourth canal about 25 percent of the time, but may also exhibit fewer canals than the first molar. Lower molars, including tooth number 18, typically have two roots with one root containing two canals and one root containing one canal. However, both roots can each contain two canals. On rare occasion, a third root is visible.
Second molars are more variable.
Some can have four canals, some three, some two, and some have only a single system. All these different canals with their various sizes and shapes can create a special challenge when treating molars. It sounds as if root canal therapy has made your tooth more comfortable. Occasionally, there is some minor soreness after root canal therapy is performed. Usually, this is mild and may only last for several hours to a few days after a root canal procedure.