Editor—Hypodontia, congenitally missing teeth, is common in modern man. The teeth most often missing in populations of European origin are the upper lateral incisors and second premolars. The condition is known to have a strong genetic component. At present two mutated genes in humans,MSX1 1 andPAX9,2 are known to cause missing permanent teeth. Mutations in MSX1can also cause orofacial clefting.3 Several experimental and clinical studies indicate that other genetic components are also involved.4-8 Hypodontia is also often seen in syndromes, particularly in those which present with other ectodermal anomalies,9 and in non-syndromic patients with cleft lip/alveolus with or without cleft palate.

The population prevalence of the common incisor-premolar hypodontia (IPH, MIM 106600) is 8-10% in healthy European children. Some or all third molar teeth are missing in one-fifth of the population,10 and missing third molars are seen in varying combinations in IPH patients and/or family members.11Family studies also indicate that peg shaped upper lateral incisors, impacted canines, rotated bicuspids, and short root anomaly (SRA) are caused by the same genetic components that cause missing incisors and premolars.12-15 The condition is inherited as an autosomal dominant trait16 with reduced penetrance and is mostly restricted to the permanent dentition. When a large number of teeth (>6) are congenitally missing, the term used is oligodontia (MIM 6044625). The prevalence of oligodontia in European populations is estimated at 0.08%,17 but this figure also includes syndromic patients.

We describe 37 Finnish patients from 34 families with several lower incisors and upper lateral permanent incisors congenitally missing. In half of the patients, the corresponding deciduous teeth had either been missing or peg shaped. An atopic condition had been diagnosed in two thirds of the patients. Occurrence of the trait within …