Ectodermal dysplasia is characterized by congenital dysplasia of ectodermaL structures, manifested as hypohidrosis (partial or complete absence of sweat glands) hypotrichosis and hypodontia or partial anodontia. Two typesHypohidrotic (Christ-Siemens-Touraine syndrome) most common type and includes dental manifestations. Hidrotic (Clouston syndrome)- no specific dental defects are seen.