One of the very common complications associated with dental injuries is root resorption, the process of degradation and loss of the hard tooth structure (i.e. cementum and /or dentine) as a consequence of osteoclastic cell’s activity which can be observed on both external and internal surfaces. The type and extent of the injury, as measured by the extent of PDL damage, appear to be the most significant predictors for root resorption as well as the presence of bacteria in the pulp or PDL space, the time interval from injury to treatment, quality of treatment, age of the patient, and stage of root development. Regarding avulsed teeth, the development of root resorption is directly related to the storage medium used before replantation and extraoral time. Assessment and diagnosis of the root resorption is usually taken place following collecting a detailed history from the patients and precise clinical examination of the affected teeth followed by utilizing advanced imaging devices. Considering the importance of the root resorption process, the main purpose of the current project is to unify different reports addressing the etiology, incidence, rate, and molecular mechanisms underlying establishment of the root resorption process, mention diagnostic approaches and related diagnostic utilities, and finally describe unique treatment approaches described so far for each subclass of this pathological event in order to update and clarify complexities associated with root resorption event following dental trauma in permanent dentition.