When we do a large filling, remove a tooth, or some other fairly invasive procedure, we "numb" up the area with "novocaine". Well, really more specifically Lidocaine or Mepivicaine . Anyways, the obvious advantage of numbing is there is no pain or discomfort related to the procedure. However, the lip, tooth, gums, and sometimes part of the tongue will be numb for a few hours. Some kids don't quite know how to deal with this numb lip. Unfortunately, some will bite their lip causing it to swell dramatically. They can't feel that they are doing damage.
Biting a numb lip thankfully does not occur that often. However, I can often spot the kid that is at risk. He is the one fiddling with his lip, sucking it between his teeth, scratching his chin and is otherwise preoccupied with the numb feeling. I always, I mean always, warn the child (and the parent) to not bite on the lip, not to pinch or scratch it either. If they do, it can take a few days for the swelling to go down. You can try an ice pack to limit the swelling in the first few hours. There is sometimes a white/yellow scab inside the lip or cheek. Thankfully, it almost always heals up within a few days. It's best to let your dentist know if you are concerned. Those are the kids to really watch the next time and to avoid numbing unless it's really necessary the next time. If we have a calm child and there is a really small cavity to be filled, there is often no need to numb up the tooth; the kids do quite well.