Root resorption is a condition in which biological or disease-related changes occur within the root of a tooth, causing loss of tooth structure. It can occur internally within the root canal or externally at the surface of the root of the tooth. Internal resorption usually begins with inflammation of the dental pulp within the root of the tooth, which eventually spreads over time and gradually erodes the tooth structure from the inside out. External resorption, on the other hand, is typically more aggressive and starts beneath the gumline with inflammation of the connective tissue that holds the tooth in place, eroding the tooth structure from the outside in toward the root of the tooth. Both types of resorption can be caused by multiple factors such as dental trauma, infection, and irritation. Resorption often does not cause obvious symptoms and is usually discovered by your doctor using x-rays or during your dental exam. If root resorption becomes too advanced or is left untreated, it can eventually lead to the loss of the affected tooth. Your doctor will work with you to determine the best course of treatment based on your unique situation.