Whether they are conventional root canal therapies or surgical procedures, both are designed to remove diseased tissue and restore teeth to a healthy state. Root canal treatment doesn't cause pain, it relieves it. In many cases, endodontic treatment relieves chronic pain from toothaches caused by pulp inflammation or infection.
Endodontic procedures are generally painless because sedatives and/or anesthetics are used to dull or eliminate nerve sensitivity. In most cases, an endodontic procedure is no less traumatic that a conventional filling.
Any mild discomfort you feel following an endodontic procedure can be minimized or eliminated by over-the-counter analgesics. If pain or undue pressure persists after a week or so, you should contact your endodontist.