A localized arrested tooth development which appears to involve most commonly the anterior teeth, usually on one side of the midline, most often the maxillary central and lateral incisors. Roentgenographically, the teeth have a ghostlike appearance. Calcification and bits of prismatic enamel may be found in the pulp and the enamel is thin and absent in part. (Jablonski, Illustrated Dictionary of Dentistry, 1982).