Some tenderness for a few days after root canal treatment is normal. Pain that is getting worse after a week, swelling, or a tooth that flares up months or years later is not, and needs looking at: it usually means infection remains or has returned in a canal that was missed, was difficult to clean, or has become re-infected through a leaking filling.
What the options are
Retreatment: the old filling is removed and the canals cleaned again. Apical surgery: a small procedure at the root tip, where retreatment through the crown is not possible or has already been tried. Extraction, where the tooth is cracked or cannot be restored. An X-ray and sometimes a CBCT scan decide which.
Your original dentist
If the treatment was recent, your treating dentist should see the tooth first; they know what was found and done. A second opinion is reasonable if the problem persists.
Dr. Preeti KaushikBDS · Dental Surgeon · Senior Associate Dentist