When a primary tooth sustains a traumatic injury, development of the permanent tooth can be disturbed, leading to various malformations. This case report details the 7-year follow-up of a developmental anomaly of a central mandibular incisor in a 10-year-old Japanese girl with a history of dental trauma that had occurred at age 4. The trauma had resulted in unusual crown dilaceration in the permanent successor, which exhibited a discoloured and abnormal crown morphology. Radiographic examination revealed crown dilaceration of the tooth, which had a curved root canal.