Dentin dysplasia is a genetic disorder of the teeth that affects the dentin and the pulp. Type I is sometimes called "rootless teeth," because of the loss of organization of the root dentin, which often leads to a shortened root length. The purpose of this article was to present a rare clinical case of a girl who was diagnosed with dentin dysplasia type I when she was referred for an orthodontic evaluation. Panoramic and periapical radiographs showed defective root formation and areas with periapical radiolucencies in several teeth. Her Angle Class I malocclusion was successfully treated, providing esthetic and functional results, without clinical symptoms or signs of periodontitis or odontogenic infections.