Abstract
Though dental clinicians frequently encounter injuries to young permanent teeth, it seems that the formation of a root in the dental socket where a young tooth fell off in trauma has not been reported.
Case 1: The formation of a root on the site of an upper right central incisor displaced in trauma was observed radiographically and histologically. The root buried under the gingiva was a bowling-pin like structure and not only had normal dentin and cementum but also cylindrical denticles, accessory canal like canalicles and cementoid tissue. It was considered that the upper portion of this root was abnormally formed under the influence of the injury and the occulusal function by a partial denture while the lower portion was originally formed by Hertwig's epitherial sheath.
Case 2: In reimplantation of an upper left incisor, the formation of a root like structure was observed over a period of time in radiography between the maxillary bone and the root apex of the reimplanted tooth. This structure was considered to arise as well as the lower portion of Case 1, i. e. a root apex.
