What is the primary cause of internal resorption in teeth?

The primary cause of internal resorption in teeth is usually in response to trauma. Internal resorption is a process where the inner structure of the tooth, particularly the dental pulp, begins to be broken down and resorbed by the body's own cells. This often occurs after an injury to the tooth, which can trigger an inflammatory response. When the dental pulp is affected, it may stimulate the odontoblasts (the cells responsible for dentin formation) to start resorbing dentin, resulting in a characteristic radiolucent area seen on radiographs.

This phenomenon typically cannot be attributed to decay or inflammatory responses from other sources. Although dental caries can lead to inflammation and secondary complications, their primary effect is external, affecting the structure of the tooth from the outside rather than triggering internal resorption. Similarly, radiolucency or radiopacity over unaltered canals does not directly indicate a cause for resorption but rather represents a consequence or a symptom observable on imaging. Hence, trauma, being the catalyst for internal resorption, is the most accurate choice.