What This Guide Covers
This guide explains internal tooth resorption, a condition where a tooth breaks down from the inside out. It covers causes, warning signs, diagnosis, and treatment options.
Internal resorption is a specific type of root resorption (the process of tooth structure being dissolved and absorbed by the body). Unlike external resorption, which starts on the outside surface of the root, internal resorption begins inside the pulp chamber or root canal. The pulp is the soft tissue at the center of your tooth that contains nerves, blood vessels, and connective tissue. [1]
This guide is written for patients who have been told they may have internal resorption, or who want to understand the condition after seeing an unusual finding on an X-ray. It is also useful for anyone who has experienced dental trauma and wants to know what long-term changes to watch for.
Because internal resorption is an endodontic condition, meaning it involves the inner tissues of the tooth, it is typically diagnosed and treated by an endodontist. You can learn more about this specialty on the endodontics page.
Understanding Internal Tooth Resorption
Internal resorption is a process in which specialized cells called odontoclasts destroy dentin and sometimes root structure from inside the tooth. It is relatively uncommon but can lead to serious structural damage if left untreated.
What Happens Inside the Tooth
In a healthy tooth, the pulp tissue lives peacefully inside the root canal and pulp chamber. It supplies nutrients and sensation to the tooth. Under normal conditions, the inner walls of the root canal are stable and do not change shape.
When internal resorption starts, something triggers the body's immune cells to become active inside the pulp. Odontoclasts, which are cells that break down hard tissue, begin eating away at the dentin lining the inside of the root canal. Over time, the canal space enlarges and the walls of the root become thinner. [1]
A 2022 review in the International Endodontic Journal described internal resorption as requiring two conditions: damage to the protective lining inside the root canal (called predentin) and ongoing inflammation in the pulp to keep the resorptive cells active. [1] Without both conditions present, the process typically does not start or sustain itself.
Internal resorption is estimated to affect roughly 0.01% to 1.6% of teeth, making it an uncommon finding. [2] It is most often discovered by chance during a routine dental X-ray, since it usually causes no symptoms in its early stages.
Causes and Risk Factors
The exact cause of internal resorption is not fully understood, but several triggers have been identified in the dental literature. [1] The most commonly cited factors include:
Dental trauma is one of the strongest associations. Injuries such as concussion, subluxation (slight loosening), lateral luxation (displacement), and intrusion (being pushed into the bone) can damage the pulp and its protective inner lining. A 2020 systematic review examining root resorption after various types of dental luxation injuries found that traumatized teeth carry a measurable risk of resorption, with the type and severity of the injury influencing the likelihood. [3]
Chronic pulpitis (long-standing inflammation of the pulp) is another recognized trigger. This can result from deep cavities, cracked teeth, or repeated dental procedures on the same tooth. [2] Certain pulp treatment procedures, particularly in primary (baby) teeth, have also been associated with internal resorption. A retrospective study of ferric sulfate pulpotomies in primary molars found internal resorption in a portion of treated teeth during follow-up. [4]
Other proposed risk factors include heat generated during dental procedures, orthodontic treatment, and certain systemic conditions, though the evidence for these associations is more limited. [2]
- Dental trauma: Blows to the mouth, falls, and sports injuries that damage the pulp tissue. [3]
- Chronic inflammation: Deep decay, cracks, or repeated restorations can cause ongoing irritation to the pulp. [2]
- Prior dental procedures: Pulpotomy (partial pulp removal), tooth replantation, or other treatments that disturb the inner lining of the canal. [1]
- Orthodontic forces: In rare cases, prolonged orthodontic pressure may contribute, though this is more commonly linked to external resorption. [2]
Types of Internal Resorption
Endodontists generally classify internal resorption into two main types based on how the tissue behaves inside the canal. [1]
The first type is internal inflammatory resorption. In this form, the resorptive cells gradually enlarge the canal in a relatively uniform, oval, or round pattern. The process is driven by inflammation and continues as long as the pulp has a blood supply feeding the resorptive cells.
The second type is internal replacement resorption. This is less common. Here, the resorbed dentin is replaced by bone-like tissue (called metaplastic bone or cementum-like tissue) inside the canal. This can make treatment more challenging because the replacement tissue may be difficult to remove during a root canal procedure. [1]
Both types can occur anywhere along the root canal, from the pulp chamber in the crown of the tooth down to the tip of the root (the apex). The location and extent of the resorption are key factors in determining whether the tooth can be saved.
Signs, Symptoms, and Diagnosis
Internal resorption often produces no symptoms in its early stages. Most cases are found during routine X-rays before a patient notices anything wrong.
What You Might Notice
In many cases, internal resorption is completely silent. You may have no pain, no sensitivity, and no visible changes to the tooth for months or even years.
The most well-known visible sign is the "pink tooth of Mummery," named after British histologist James Howard Mummery. This occurs when the resorption has progressed enough to thin the outer enamel and dentin, allowing the reddish, blood-rich granulation tissue inside to show through. The result is a pinkish discoloration on the crown of the tooth. [6] This sign is distinctive but not always present. Many cases of internal resorption never produce a pink spot because the resorption remains deep within the root.
If resorption advances significantly, you might develop a dull ache or sensitivity. In advanced cases where the root wall has been perforated (a hole forms through the side of the root), you may notice localized gum swelling or tenderness. However, these symptoms typically appear only in later stages.
How Endodontists Diagnose Internal Resorption
Diagnosis relies heavily on dental imaging. On a standard two-dimensional X-ray (periapical radiograph), internal resorption typically appears as a well-defined, round or oval radiolucency (dark area) within the root canal. The borders of the dark area are usually smooth, distinguishing it from the irregular borders often seen with external resorption. [1]
One important diagnostic feature: the resorptive defect does not move position when the X-ray angle is changed. This is called the "buccal object rule" or Clark's technique, and it helps differentiate internal resorption from external resorption, which will appear to shift. [1]
Cone-beam computed tomography, commonly called CBCT, is a three-dimensional imaging tool that has significantly improved the diagnosis of resorption. CBCT provides cross-sectional views of the tooth, allowing the endodontist to see the exact location, size, and extent of the resorption. It can also reveal whether the root wall has been perforated. Patel et al. noted in their 2022 review that CBCT is particularly valuable for treatment planning in resorption cases because it provides information that two-dimensional X-rays simply cannot. [1]
Pulp vitality testing (checking whether the nerve inside the tooth is alive) also plays a role. In internal inflammatory resorption, the tooth typically still tests vital because a blood supply is needed to sustain the resorptive process. If the pulp dies on its own, the resorption usually stops because the cells lose their nutrient supply. [1]
Treatment: What to Expect
Root canal treatment is the standard approach for internal resorption. The goal is to remove the resorptive tissue and fill the canal space to prevent further damage. [1]
Root Canal Therapy for Internal Resorption
The treatment process follows the same general steps as a conventional root canal, with some modifications for the resorptive defect.
First, the endodontist administers local anesthesia to numb the area. A small access opening is made in the crown of the tooth. Next, the inflamed or necrotic pulp tissue is carefully removed from the canal. The resorptive granulation tissue (the soft, blood-rich tissue causing the destruction) is also removed. Sodium hypochlorite, the irrigating solution used during root canals, is particularly effective here because it dissolves organic tissue and helps clean the irregularly shaped resorptive cavity. [1]
Thorough disinfection and shaping of the canal follow. Because the resorptive defect creates an irregular enlargement in the canal, the endodontist may use warm or thermoplasticized gutta-percha (the rubber-like filling material) to fill the space more completely. In some cases, a bioceramic sealer or mineral trioxide aggregate (MTA) may be used, especially if a perforation exists. [1]
The critical principle is that removing the blood supply to the resorptive cells stops the process. Once the pulp tissue is gone, the odontoclasts can no longer survive, and the resorption halts. [1] In many cases, this is enough to save the tooth long-term, though results vary based on how much tooth structure remains.
When the Resorption Is Advanced
If CBCT imaging shows that the resorption has perforated the root wall, treatment becomes more complex. The endodontist may still attempt root canal treatment with the use of biocompatible repair materials like MTA to seal the perforation. [1]
In cases of internal replacement resorption, the bone-like tissue deposited inside the canal can be difficult to remove with standard instruments. The endodontist may need to use ultrasonic tips or other specialized tools to clear this hard tissue before filling the canal. [1]
If the resorption has destroyed too much of the root structure, the tooth may not be salvageable. In these situations, extraction followed by tooth replacement (such as a dental implant or bridge) may be the most appropriate option. This is one reason early detection is so valuable; it gives the endodontist more remaining tooth structure to work with.
After root canal treatment, the tooth will typically need a permanent restoration. In most cases, a crown is recommended to protect the remaining weakened tooth structure. Your endodontist and general dentist will coordinate on the final restoration plan.
Follow-Up and Monitoring
After treatment, periodic follow-up X-rays are needed to confirm that the resorption has stopped and the area around the tooth is healing. Your endodontist will typically schedule a follow-up visit at 6 to 12 months and may continue monitoring annually for several years.
If internal resorption is found early and treated before significant structural loss, the long-term outlook is generally favorable. [1] However, teeth with extensive resorption or perforations have a less predictable prognosis. Your endodontist will discuss realistic expectations based on your specific case.
Cost Considerations
Treatment costs for internal resorption vary depending on the tooth involved, the complexity of the case, and the type of restoration needed afterward.
Root canal treatment on a front tooth (which has a single canal) typically costs less than treatment on a molar (which has three or four canals). When internal resorption is present, the procedure may take longer or require additional materials such as MTA, which can increase the fee. Costs vary by location, provider, and case complexity. In the United States, root canal treatment generally ranges from $700 to $1,500 or more for a single tooth, not including the crown or other final restoration.
A CBCT scan, if needed for diagnosis and treatment planning, typically adds $150 to $500 to the overall cost. Some endodontic offices include this imaging in the consultation fee, while others charge separately. Costs vary by location, provider, and case complexity.
Dental insurance often covers a portion of root canal treatment and the subsequent crown, though coverage levels differ widely among plans. It is a good idea to contact your insurance provider before treatment to confirm your benefits. If the tooth requires extraction instead, the cost of replacement options such as dental implants or bridges should also be factored into your planning.
When to See an Endodontist
You should see an endodontist whenever internal resorption is suspected or confirmed on an X-ray. General dentists may detect the condition, but endodontists have specialized training and tools to manage it.
Endodontists complete two to three years of additional training beyond dental school, focused specifically on diagnosing and treating conditions of the dental pulp and root. They routinely use advanced imaging such as CBCT and operating microscopes, which are critical for accurately assessing resorption cases. [5]
Your general dentist may refer you to an endodontist if a routine X-ray shows an unusual dark area inside the root canal, if a tooth has developed an unexplained pink discoloration, or if you have a history of dental trauma and a tooth begins behaving unusually. These are all situations where specialty evaluation is appropriate.
Even if you are not experiencing symptoms, a referral for evaluation is worthwhile. Internal resorption that is caught while the defect is small and the root walls are still intact has a much better treatment outcome than resorption that has been allowed to progress. [1] Routine dental visits with periodic X-rays remain the most reliable way to catch this condition early. [7]
Find an Endodontist Near You
If you or your dentist suspects internal resorption, consulting an endodontist is the next step. An endodontist can provide a thorough evaluation with advanced imaging and recommend the best course of action for your specific situation. You can search for a qualified endodontist in your area on the endodontics page at My Specialty Dentist.
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