A root canal is read as reaching deep to deal with a pain at its source. Tradition sees it as an uncomfortable but thorough repair of something that has been aching quietly for a long time.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.