Root resorption (RR) is a common complication of traumatic dental injuries (TDIs), which could result in tooth loss and affect life in severe cases. The management of a traumatized tooth with RR remains a challenge for clinicians. In our presented cases, the impacted teeth had a history of trauma and underwent thorough non-surgical endodontic treatment; however, RR still occurred months later and could be observed through a periapical radiograph. Therefore, root canal therapy was performed under a dental microscope with a quick-setting calcium silicate cement to repair the RR site. After a long follow-up, the affected teeth showed almost complete healing of the periradicular tissues without sign of RR. This report demonstrates that external root absorption is typically a consequence of traumatized teeth. However, to date, there is still no effective method for its treatment. Here, we successfully applied microscopical surgery to the traumatized teeth experiencing root absorption and provided them with a new healing opportunity.