Root canal treatment is needed when the nerve supply of the tooth is infected through decay or injury. You may not feel any pain in the early stages of the infection. In some cases your tooth could darken in colour, which may mean that the nerve of the tooth is dying or has died. This is when root canal treatment is necessary. A root canal does not normally hurt. It is very similar to a filling appointment, only takes a little more time as more of the tooth is being “filled” or restored.