After you have oral surgery, a dental implant or an extraction, there is going to be some amount of swelling. Depending on your immune system, you can experience some swelling even after a root canal treatment, or a filling that is deeper. This is completely normal, as the gums are basically an organ, and they are part of your immune system, so it is only natural and healthy that they would react to outside stimulus, especially to being cut or otherwise removed, by swelling up. This is done to quell bleeding but also to engorge the area and make it larger.
When it is bad
After oral surgery and even after a serious root canal where antibiotics had to be administered, the end result can be swelling that is quite scary and quite big. Sometimes it may even look like a golf ball or a peach even is inside of your cheeks. This is normal, and even the side of your face swelling up to three or four times its size is normal. The problem is if it does not go down. The swelling should start to subside after 48 hours, and should be much better in 72 hours. If after 3 days you still have a swelling that is just as big, or if the swelling did not go down but is still growing after 48 hours, you may have a problem. This is also no cause for concern, but it is a reason to call your dentist and ask them what is wrong. If the swelling is hot, painful or itchy, you have an infection and need to contact an emergency dentist immediately and get emergency medical care.
Swelling and discoloration
When getting certain dental procedures you may bruise. This is especially the case with extractions where quite a lot of force may need to be exerted to remove the tooth from the socket it is in. If there was bruising to being with, then discoloration is no problem. The site of the swelling and even the outside of the skin may be bruised and purple, but that is normal. The skin may turn red from being hot and bothered and this is also normal, but the redness should go away in 12 hours at the most. A red swollen cheek is a sure sign of an infection, and you will need to contact your dentist immediately. If there is no bruising and the change of color starts after the swelling is going down, you are definitely in need of medical help.