American Board of Orthodontics (ABO) Practice Exam

External resorption is a process in which the external surface of the tooth root is broken down and lost, and it often occurs in specific conditions related to trauma or treatment. Orthodontic treatment can lead to external resorption due to the biological response of the periodontal ligament and surrounding structures to the forces applied during tooth movement. When teeth are moved, especially when significant forces are involved, there can be an adverse localization of the resorptive process, leading to loss of tooth structure.

Additionally, endodontic issues, such as a prolonged or severe infection, can trigger external resorption by causing inflammatory mediators to affect the cementum and alveolar bone. In such cases, the body responds to the presence of inflammation or damage in a way that can lead to the resorption of root surface tissue.

While intrusive trauma, bone loss due to infection, and excessive orthodontic forces can also contribute to resorptive events, they do not comprehensively cover the broader spectrum of conditions associated with the resorptive changes seen in clinical practice as directly as orthodontic treatment and endodontic problems do. This is why orthodontic treatment or endodontic issues are recognized as key factors in the occurrence of external resorption.