A radiograph reveals an area of external resorption. What is the typical cause?

External resorption is a process where the outer structure of a tooth's root is broken down and absorbed by the body, typically indicated by a radiographic finding. The most common cause of external resorption is chronic trauma. This trauma can result from various factors, including repetitive mechanical stress on the tooth, such as from grinding or clenching, or repeated trauma to the same area that stimulates the resorption process. Over time, this continual stress can lead to cellular activity that breaks down bone and tooth structure externally.

In contrast, internal resorption occurs from the inside of the tooth and usually results from pulp inflammation or infection, which leads to the breakdown of dentin and pulp tissue. Short-term pulpitis may lead to temporary changes in the tooth, but it is not typically associated with external resorption. Similarly, while malocclusion can cause issues with a tooth’s position and alignment, it is less frequently a direct cause of external resorption compared to chronic trauma. Thus, chronic trauma is the most accurate explanation for the cause of external resorption as found in the question.