This can vary greatly and is usually determined by the severity of the problem with which you present.  In most cases if post operative pain occurs, it is usually within the first 24-48 hours after treatment and will usually involve tenderness to pressure on the treated tooth (like a strong bruise).  If your tooth is going to be tender, it is usually most tender when it wakes up after anesthesia, so we recommend anti-inflammatories (Advil/ibuprofen, Aleve, aspirin, Motrin, Nuprin, etc.) to be taken beforethe anesthesia wears off.  If your endodontist feels it’s warranted, you may be given a prescription for pain that can be taken along with the anti-inflammatory if needed.  If you present with an infection, you may continue to have discomfort with your tooth until the prescribed antibiotics have a chance to affect the area, which usually takes about two days.  Having said all of that, understand that our purpose is to get you out of pain, and the vast majority of our patients feel muchbetter after treatment.