“What are the signs that a root canal is needed?”

First, an X-ray is needed to determine if there is infection in the tooth. Then, the tooth is aching and has lingering responses to hot and cold. Also will have spontaneous pain. Sometimes lack of response to cold is an indication of a dead tooth, which also needs a root canal.
Hope this helps.

1. Extreme pain associate with fractured or infected tooth.
2. Constant dull pain
3. Fractured tooth or infected tooth structure is in close proximity to the nerve structure.
4. The nerve is dead.
Please visit your dentist for definitive diagnosis and treatment. Good luck, hope you feel better soon.