Severe Pain in Gum After a Root Canal of a Dead Tooth?

When doing root canals on non vital teeth like yours . You have alot of potential for flareups which means over the first 24 - 72 hours you can have more pain than you came in with.  If your dentist did the price due without nova sine,  it sounds like they did not use a rubber dam. By not isolating the tooth with a rubber dam.  Your tooth may have become inoculated by bacterial from your saliva.   So bacteria that are normally outside the tooth are now inside the tooth.   This can lead to an acute infection.   With your antibiotics you should be taking 800 mg of ibuprofen 3 times aday. 

This will help reduce your discomfort and swelling from an acute infection. We recommend all patients to take ibuprofen , for three days after a root canal with or without pain.  If your pain does not subside after a few days you may need to add a second antibiotic. 

Although a crack was not seen, you should know cracks and fractures are very hard to detect on x-rays. There could be an infection but it will not appear on an xray for 10 days. I recommend you see your dentist again in 10 days from your last visit.

How horrible for you to be undergoing this pain! It may be that there is a fracture that cannot be detected with an x-ray. The x-ray is a two dimensional film, if the fracture is in the same plan it won't be visible, It is probably also too soon for other changes to be detected on an x-ray, for example it takes a while to see changes in the bone, have to lose enough that it is visible in the two dimensional film, Are you seeing a root canal specialist? IF not that would be the next step. Good luck, hope your pain resolves soon! Bernice Szafarek DMD