When should i notice improvement of post-root canal swelling (2days after procedure) now that i've started amoxicillin?

Within 36 hours: I find that between 20 to 36 hours you should note a noticble decrese in swelling. If this is not the case please contact your dentist to change the type of antibiotic or open the tooth to drain further. If the swelling greatly increases you may need to go to the emergency room. This can be dangerous.

2-3 days: If the swelling is not too large and aggressive, antibiotics will most often be carried by capillaries to the source of infection. However, if the infection is growing quickly the antibiotic carried by the blood stream can't get to the source. At that point, only an incision to drain will help.

36 to 72 hours: An infection sometimes takes a couple of days to allow the antibiotic to begin to work. Application of heat will increase the swelling, best to just let the drug to work, .