Root resorption is a biological process where the body’s own cells break down and dissolve the root structure of a tooth. This condition involves the progressive loss of dentin and cementum, the hard tissues that make up the root, through the action of specialized cells called odontoclasts. The process can affect both primary (baby) teeth and permanent teeth. While it is a normal function that allows baby teeth to fall out, its occurrence in permanent teeth is a pathological issue that can lead to significant dental problems.
Types of Root Resorption
Root resorption in permanent teeth is categorized based on where the process begins. The two main types are internal and external resorption. The origin of the resorption dictates the progression and treatment approach, as each type has a distinct pattern of tooth structure loss.
Internal resorption starts from within the pulp canal, the chamber inside the tooth containing nerves and blood vessels. In this form, inflammation within the pulp tissue triggers cells to begin dissolving the dentin from the inside out. This process can create a hollow, balloon-like enlargement of the root canal space. Because it originates internally, it may not be visible from the outside of the tooth until it has progressed significantly.
External resorption, the more common of the two, begins on the outer surface of the tooth root. This process is initiated in the periodontal ligament, the tissue that connects the tooth to the jawbone. From the outside, cells start to eat away at the cementum, the protective outer layer of the root, and then move inward toward the dentin. There are several sub-types of external resorption, often classified by their specific cause and location on the root.
Primary Causes and Risk Factors
Root resorption is triggered by events that damage the protective layers of a tooth’s root. For the process to begin, the unmineralized tissues lining the root—predentin on the inside and precementum on the outside—must be compromised. A persistent stimulus like inflammation or pressure then activates clastic cells to begin their destructive work.
Orthodontic treatment, such as braces, is a well-documented risk factor. The mechanical forces used to move teeth can sometimes be excessive, causing inflammation in the periodontal ligament and leading to external root resorption. While a minor amount of resorption is a common side effect of moving teeth, significant damage can occur if the forces are too heavy or applied for too long.
Physical trauma or injury to a tooth is another primary cause that can lead to either internal or external resorption. A direct blow can damage the blood supply to the pulp, causing chronic inflammation that initiates internal resorption. The same injury can also damage the periodontal ligament on the outside of the root, creating a site for external resorption to begin. Even low-grade, chronic trauma from habits like teeth grinding can contribute to the process over time.
Pressure from adjacent structures, such as an impacted wisdom tooth, a cyst, or a tumor, can also cause external resorption. The constant force exerted by an impacted tooth can physically wear away the root of the neighboring tooth. Similarly, chronic inflammation stemming from an infected pulp (pulpitis) or advanced periodontal (gum) disease can trigger an inflammatory response that leads to resorption. In these cases, bacterial infection acts as the persistent stimulus that fuels the clastic cells.
Identification and Diagnosis
Root resorption is often called a silent disease because it is asymptomatic in its early stages and discovered incidentally during routine dental X-rays. Since pain is not a common early symptom, patients are often unaware of the condition until it has advanced significantly.
When symptoms do appear, they can vary depending on the type and severity of the resorption. For internal resorption, a classic sign is a pinkish discoloration on the tooth’s crown, known as the “pink tooth of Mummery.” This occurs because the resorption process thins the dentin, allowing the highly vascular, inflamed pulp tissue to show through the enamel. Other potential symptoms for both internal and external resorption may include pain, swelling of the gums, or a tooth becoming loose.
A definitive diagnosis begins with a thorough clinical exam and standard periapical X-rays. These two-dimensional images can often reveal the characteristic radiolucent (dark) areas on the tooth root where tissue has been lost. To differentiate between internal and external resorption, a dentist may take multiple X-rays from different angles. If the dark spot appears to move relative to the root canal when the angle is changed, it suggests external resorption.
In complex cases, a more advanced imaging technique called Cone-Beam Computed Tomography (CBCT) may be necessary. A CBCT scan provides a detailed, three-dimensional view of the tooth and surrounding bone. This allows the clinician to determine the precise location, size, and extent of the resorptive defect for accurate diagnosis and treatment planning.
Available Treatment Pathways
The approach to treating root resorption depends on its type, location, and severity. The primary goal is to remove the stimulus causing the resorption and repair the damage to preserve the tooth. Early detection leads to a better prognosis, as treatment is more effective before the tooth’s structural integrity is severely compromised.
For internal resorption, the standard treatment is root canal therapy. Since the resorption is driven by inflamed or infected tissue within the pulp canal, removing this tissue effectively stops the process. During a root canal, the endodontist cleans out the entire pulp chamber and canal system, eliminating the blood supply to the destructive clastic cells. The cleaned space is then disinfected and filled with a biocompatible material to seal it from further infection.
Treating external resorption is often more complex because the cause is external to the tooth. If the resorption is caused by orthodontic forces or pressure from an impacted tooth, the first step is to remove that stimulus. For small, accessible lesions on the root surface, a surgical procedure may be performed where the gum is lifted to expose the defect, the resorptive tissue is removed, and the area is repaired with a filling material.
If the external resorption has progressed and involves the pulp, root canal therapy may be required in addition to surgical repair. In some cases where the damage is very extensive and has severely weakened the tooth structure, saving the tooth may not be possible. When a tooth is deemed non-restorable, extraction becomes the only viable option to prevent further complications like infection or fracture.