External vs. Internal Resorption
There are 2 types of resorptions: Internal and external.
Internal resorption is a process by which the resorptive defect originates from inside going into the canal system. Depending on the stage when this is discovered, the pulp may be vital or necrotic.
Radiographically, it presents as a smooth defect that centers around the canal. This can be easily discerned with CBCT. If caught early, and no perforation is observed, this can be treated with a root canal therapy. Internal resorption is relatively rare.
Internal desorption is canal dentinal wall destruction from the inside of the canal. Usually this is from trauma: for example, luxation, excessive orthodontic forces. Radiographic presentation is usually a smooth bulbous RL centered in the canal area. Normally, if the case is not severe, a shift shots radiograph will discern the location. Pulp is usually vital, but may become necrotic over time. EPT and cold testing may give conflicting testing results.
Treatment is RCT. In a more severe case where the internal resorptive defect is large enough to perforate the root into the surrounding osseous area, treatment is more challenging and prognosis is not ideal.
Here a 56YO hispanic male present to the clinic with a small sinus tract at the apical area of #4. Diagnosis was RCT tooth with chronic suppurative asymptomatic apical abscess. Non-surgical retreatment was recommended.
Extreme internal resorption. 23 YOAF presented to clinic with no discomfort or symptoms. No significant clinical findings noted. But here the PA radiograph showed extensive internal root canal resorption. Patient was very concerned about her anterior aesthetics and wanted to save this tooth for as long as possible. RCT was intiated. I informed her that if there is a communication with the external osseous area, then the prognosis is poor.
RCT was initiated. No root perforation was noted, canal system was cleaned and irrigated with disinfectant. Intra-appointment Ca(OH)2 was placed. Apical canal was then obturated. The resoprtive defect was then filled with a composite. The coronal 1/3 of the canal was then sealed with a flowable composite.
This is a case where I normally would discuss the option of extraction and implant replacement. However, patient was young and was very concerned about aesthetics and losing her tooth. Thus, we agreed to try saving the tooth.
External resorption is more common. We really are not certain what causes it although dental trauma is a strong possibility. I often see is external resoprtion that start at the CEJ and it burrows its way into the tooth, but the pulp is initially spared until much later on. If not stopped, it will advance further into the tooth and eventually destroys the tooth. Treatment is usually surgical repair, and if the defect is close to the pulp, RCT may also be necessary.