The epidemiology, aetiology, and histopathology of developmental enamel defects in human teeth
The prevalence of developmental enamel defects in t11 permanent dentition was investigated in a sample of 2923 East London schoolchildren aged 5 to 15 years. Enamel discolourations and hypoplasias were identified using well defined criteria. Two-thirds of the children had at least one tooth with- an enamel defect. In the group of 1518 children with 24-28 erupted permanent teeth, 68 per cent had enamel defects with. a mean of 3.6 per child. The upper central Incisors and first molars had the highest prevalence of enamel defects. In these teeth., the proportion of defects decreased with.. age. The majority of defects were discolourations; 67 per cent of children..with a "complete" -permanent dentition had discolouration defects whereas only iS. per cent had enamel bypoplasia. The aetiology of defects-found in children with. two or more hypoplastic teeth was investigated in a family study. Four of the 101 index cases had amelogenesis imperfecta and 18 had chronological hypoplasia caused by systemic diseases. The defects in a further 18 subjects had a probable systemic aetiology. Bilateral hypoplasia of the lower incisors was found in 22 subjects and a multifactoria]. mode of inheritance was postulated for this condition. For one third of the index cases no cause could be found for their hypoplasia. A histological study. complemented thesurveys by describing structural characteristics of different types of enamel defects. The investigation highlighted a number of differences between enamel defects caused by systemic upsets and those caused by genetic factors. An archaelogical. study assessedthe prevalence-of enamel h-ypoplasia in a cällection of early British skulls. Thirty-seven per cent had a number of hypoplastic teeth. There were few severe cases of hypoplasia; the most common type of defect being shallow horizontal grooves. The many teeth with shallow defects suggested periodic disturbances in enamel formation between 2 and 6 years of age. This thesis has provided further information about the complex nature of enamel defects. The different aspects of enamel defects which have been investigated have contributed to a greater understanding of their prevalence, aetiology and histology.