The cost of root canal varies with the number of canals needing treatment. Canals vary with tooth type, on average ranging from your front teeth with 1-2 canals, to your back molars with 3-4 canals. Each fragile canal needs to be carefully cleaned, medicated and filled, requiring a lot of time, precision, materials and medication to treat the tooth successfully. Even in the best of circumstances, root canal therapy is never 100% guaranteed success depending also on how your body reacts to the treatment over time.