[The mentally retarded dental patients. Who are they?].

More than 30,000 Norwegians are mentally retarded and about 50% of them are severely retarded and often multihandicapped. Before 1975 the majority of the severely retarded resided in large institutions. New legislation has led to an increasing emphasis on decentralization and integration in local communities. Mental retardation is caused by prenatal brain damage in 90% of the cases. Chromosomal aberrations like Down and Fragile-X syndromes are the most common causes. A high proportion of individuals with autism, cerebral palsy, epilepsy and sensory defects are mentally retarded, and the most common additional diagnoses in mental retardation are speech defects, epilepsy, cerebral palsy, congenital heart disease, sight and hearing impairment and hydrocephalus. Almost 1/3 of the mentally retarded adults have developed psychiatric disturbances. Families with mentally retarded children are affected emotionally, socially and economically, and the burden increases as the mentally retarded individual grows older.