Etiology of different types of root resorption requires two phases: mechanical or chemical injury to the protective tissues and stimulation by infection or pressure. Injury can be similar in various types of root resorption. The selection of proper treatment is related to the stimulation factors. Intrapulpal infection is the stimulation factor in internal root resorption and external periradicular inflammatory root resorption. Adequate root canal treatment controls intrapulpal bacteria and arrests the resorption process. In cervical root resorption, infection originates from the periodontal sulcus and stimulates the pathological process. As adequate infection control in the sulcus is unlikely, removal of granulation tissue from the resorption lacuna and sealing are necessary for repair. Removal of the stimulation factor, i.e. pressure, is the treatment of choice in root resorption related to pressure during orthodontic treatment, or an impacted tooth or tumor. In ankylotic root resorption, there is no known stimulation factor; thus, no predictable treatment can be suggested. Therefore, various types of root resorptions can be classified according to the stimulation factors: pulpal infection resorption, periodontal infection resorption, orthodontic pressure resorption, impacted tooth or tumor pressure resorption, and ankylotic resorption.