Introduction: this systematic review evaluated radiographic methods that allow to detect external root resorption (err) in orthodontics, to determine adequate time intervals for control radiographs, and to identify radiographic characteristics of err. Materials and methods: we carried out systematic electronic and manual searches in databases, without year restrictions, limited to papers in Spanish or English. We included cohort studies and randomized clinical trials performed on human subjects that assessed orthodontic movement with fixed appliances that recorded root resorption before or during the course of treatment. Two authors evaluated the articles independently and extracted the ones to be selected in a standardized format. Results: the initial search yielded 285 references. 40 articles that could be related to the topic were then identified by title and abstract. After the evaluation using the inclusion criteria, 26 articles were analyzed. Due to the heterogeneity among the articles, it was not possible to estimate a global measurement for the research questions. Conclusion: the ideal method for the detection of external root resorption (err) caused by orthodontic treatment is the cone-beam tomography, however periapical radiographies may be a useful tool. When such radiographies are used as a diagnosis method, they must be taken with a 6-month periodicity and the decrease in root length must be evaluated.