This report presents three cases of separated root tip formation following traumatic injury with or without inflammation. The first case showed continued separate apical root formation; however, development of the main root with bony ingrowth was absent. The second case showed that separated root formation continued under the 2-year inflammatory conditions, even after apexification. The third patient showed partially connected root tip formation after apexification. By summarizing previously reported similar cases, we assessed the injury type, prevalence age, treatment performed and pattern of root development. This phenomenon may be elucidated by the special features of the apical papilla (AP). Understanding the capability of AP could help with treatments, such as regenerative endodontic procedures and trauma management for immature permanent teeth.