What Is Tooth Resorption?
Tooth resorption is a process in which cells in the body break down and dissolve part of a tooth. This is normal for baby teeth, which resorb as the permanent teeth push them out. In permanent teeth, however, resorption is abnormal and can lead to structural weakening, infection, and eventual tooth loss if not treated.
Resorption can affect any part of the tooth root or internal structure. It is classified by where the process begins: internal resorption starts within the pulp chamber or root canal, and external resorption starts on the outer surface of the root. Both types are progressive, meaning they will continue to destroy tooth structure until treated or the tooth is lost.
Internal vs External Resorption
Understanding which type of resorption is present is critical because the causes, progression, and treatment options differ significantly.
Internal Resorption
Internal resorption begins inside the tooth, within the pulp chamber or root canal. Inflammatory cells in the pulp tissue become activated and start dissolving the dentin (the hard layer beneath the enamel) from the inside out. The pulp must be alive, at least partially, for internal resorption to occur.
On an X-ray, internal resorption appears as a well-defined, round or oval dark area within the root canal. It looks like the canal has ballooned outward in one spot. Internal resorption is relatively rare compared to external resorption.
Causes include trauma to the tooth, extensive dental work, chronic pulp inflammation, and sometimes no identifiable cause. If left untreated, the resorption continues until it perforates the root, making the tooth much harder to save.
External Resorption
External resorption begins on the outer surface of the root. Cells in the periodontal ligament (the tissue that connects the tooth to the surrounding bone) become activated and start dissolving the root surface. There are several subtypes, each with different causes and behaviors.
- Surface resorption: Small, self-limiting areas of root surface breakdown that often heal on their own. Commonly seen after minor trauma or orthodontic treatment.
- Inflammatory resorption: Occurs when an infection or chronic inflammation near the root tip triggers ongoing breakdown of the root surface. Often associated with infected pulp tissue or a periapical abscess.
- Replacement resorption (ankylosis): The tooth root is gradually replaced by bone. The tooth fuses to the surrounding bone, loses its normal slight mobility, and eventually the root disappears entirely. This is most commonly seen after a tooth has been knocked out and reimplanted.
- Cervical resorption: Begins at or near the gum line (the cervical area of the tooth) and can spread extensively within the tooth before becoming detectable. It may appear as a pinkish spot on the tooth where resorbed dentin shows through the enamel.
What Causes Tooth Resorption?
The exact trigger for resorption is not always identifiable. However, several factors are known to increase the risk.
Dental Trauma
A blow to the face or a fall that injures a tooth is one of the most common triggers for resorption, both internal and external. The trauma damages the protective layer on the root surface (cementum) or the pulp tissue, triggering the body's resorptive response. Teeth that have been knocked out and reimplanted are at particularly high risk for replacement resorption.
Orthodontic Treatment
Orthodontic forces applied to move teeth can cause mild external root resorption, especially at the root tips. In most patients, this is minor (1 to 2 millimeters of root shortening) and does not affect the long-term health of the tooth. In a small percentage of patients, the resorption is more significant. Your orthodontist monitors for this with periodic X-rays during treatment.
Chronic Infection or Inflammation
Untreated cavities that reach the pulp, failed root canals, or chronic periodontal disease can create ongoing inflammation near the root, triggering external inflammatory resorption. Treating the source of infection is the first step in stopping this type of resorption.
Other Contributing Factors
- Impacted teeth pushing against the roots of neighboring teeth
- Cysts or tumors near the tooth root
- Teeth whitening procedures (rarely, internal bleaching has been linked to cervical resorption)
- Genetic predisposition, though this is not well understood
- Systemic conditions that affect bone metabolism, in rare cases
Symptoms and Diagnosis
One of the challenges with tooth resorption is that it often produces no symptoms until the condition is advanced.
Symptoms to Watch For
In early stages, resorption is typically painless and invisible. As it progresses, you may notice one or more of the following signs.
- A pinkish or dark spot on the tooth, especially near the gum line (cervical resorption showing through the enamel)
- The tooth becoming slightly loose without an obvious cause
- Dull pain or sensitivity, particularly if the resorption is near the nerve or has caused infection
- Swelling or tenderness in the gum near the affected tooth
- No symptoms at all, with the condition found only on a routine X-ray
How Resorption Is Diagnosed
Routine dental X-rays (periapical radiographs) are the most common way resorption is discovered. On a standard X-ray, internal resorption appears as a dark, well-defined area inside the root canal. External resorption may appear as an irregular or moth-eaten area on the outer root surface.
Cone-beam computed tomography (CBCT) provides a three-dimensional view of the tooth and is the gold standard for evaluating the extent of resorption. CBCT shows exactly where the resorption is, how deep it has progressed, and whether the root has been perforated. This information is critical for treatment planning. Endodontists routinely use CBCT for resorption cases.
Treatment Options for Tooth Resorption
Treatment depends on the type of resorption, how far it has progressed, and whether the tooth can realistically be saved.
Treating Internal Resorption
The standard treatment for internal resorption is root canal treatment. Because internal resorption requires a living pulp to progress, removing the pulp stops the resorption immediately. The endodontist cleans the canal system, fills the resorbed areas with a biocompatible material (such as mineral trioxide aggregate or gutta-percha), and seals the tooth.
If the resorption has perforated the root wall, the endodontist may repair the perforation with mineral trioxide aggregate (MTA) during the root canal procedure. The success of treatment depends on whether the perforation can be adequately sealed.
Treating External Resorption
Treatment for external resorption varies by subtype. Inflammatory external resorption often responds to root canal treatment, which removes the source of inflammation inside the tooth. Surface resorption that is minor and self-limiting may only need monitoring.
Cervical resorption may require surgical access: the periodontist or endodontist lifts the gum tissue, removes the resorptive tissue, and restores the damaged area with a filling material. For replacement resorption (ankylosis), there is no reliable treatment to stop the process once it is established. The tooth may remain functional for years but will eventually be lost as the root is replaced by bone.
When Extraction Is Necessary
If resorption has destroyed too much of the root or has perforated the root in a location that cannot be repaired, extraction may be the only option. After extraction, the tooth can be replaced with a dental implant, bridge, or removable partial denture. Your endodontist or oral surgeon will discuss replacement options with you.
Prognosis: Can a Resorbing Tooth Be Saved?
The prognosis depends on early detection and the type of resorption. Internal resorption caught before root perforation has a good prognosis with root canal treatment. Once perforation occurs, the success rate drops, though modern materials like MTA have improved outcomes for perforated cases.
External inflammatory resorption also responds well to treatment when caught early. Cervical resorption cases can often be treated successfully if the lesion has not spread too far into the tooth. Replacement resorption has the least favorable prognosis because there is no reliable way to stop the ankylosis process.
Regular dental checkups with X-rays are the best way to catch resorption early. Patients who have experienced dental trauma, undergone orthodontic treatment, or had teeth reimplanted should mention these factors to their dentist so that monitoring can be prioritized.
When to See an Endodontist
An endodontist is the specialist most qualified to diagnose and treat tooth resorption. Endodontists have 2 to 3 years of additional training beyond dental school, focused on conditions inside the tooth and root. They routinely use CBCT imaging and dental operating microscopes, which are essential tools for evaluating and treating resorption.
If your general dentist suspects resorption on an X-ray, a referral to an endodontist for a CBCT scan and evaluation is the standard next step. The endodontist can determine the type, extent, and treatability of the condition and discuss your options.
Find an Endodontist Near You
Every endodontist on My Specialty Dentist has verified specialty credentials. Search by location to find endodontists in your area, compare their experience, and schedule a consultation.
Search Endodontists in Your Area