Enamel Hypoplasia is the most common abnormality of development and mineralization of human teeth. The lesion is characterized by a quantitative defect in enamel tissue resulting from an undetermined metabolic injury to the formative cells – the ameloblasts. Clinically, enamel hypoplasia is seen as a roughened surface with discreet pitting or circum- ferential band –like irregularities which posteruptively acquire a yellow brown stain. Enamel hypoplasia is endemic in many countries of the world and is commonly reported in association with disease of childhood.
Some years ago population surveys in several countries showed that 3-15% of children exhibited some degree of enamel Hypoplasia in permanent teeth. However, the incidence of this lesion is significantly higher in vitamin D deficiency, hereditary vitamin D dependency rickets, hypoparathyroidism, and a wide spectrum of prenatal disorders. Earlier repots which implicated German measles (Rubella) during pregnancy as a major factor in enamel hypoplasia have been definitely disproven.
A specific type of enamel hypoplasia of primary teeth called linear enamel hypoplasia (LEH) is common in some economically underdeveloped countries. For example, its prevalence has been reported to be about 30-40% in Guatemala and in parts of the Caribbean coast. In children, who have signs of severe malnutrition, linear hypoplasia was present in up to 73%of the population. Enamel Hypoplasia resembling the linear type has been reported in association with acute diarrheal disease in preschool Apache Indian children. Although the pathophysiology of LEH is undetermined, many authors have suggested the synergistic action of malnutrition and infection as the most probable causative factors. A more probable factor is hypocalcemia induced by gastrointestinal diarrhea.
Hypocalcaemia It is a specific Cause of Enamel Hypoplasia. Recently evidence has suggested that the etiology of enamel hypoplasia is highly specific. Enamel Hypoplasia is seen in children having disorders of calcium homeostasis but it is not seen in children having phosphate homeostasis. It is not seen in children having hypophosphatemia 9X-linked hypophosphatemic rickets).this proves that serum phosphate level does not effect the enamel but in the conditions where hypocalcaemia is the major symptom like diarrhea etc the enamel Hypoplasia is coonly seen. This all proves that low Calcium level in serum is one of the major cause of enamel hypoplasia.
Enamel Hypoplasia and Caries Enamel Hypoplasia is clinically significant not only because it is disfiguring and the restorative treatment costly, but because it may affect caries susceptibility. There was a strong correlation between hypoplasia in the teeth of British schoolchildren (which she thought was caused by vitamin D deficiency) and caries susceptibility. For example, out of a collection of 1,500 extracted teeth, 74% of very hypoplastic teeth were carious, whereas 80% of the nonhypoplastic teeth were caries – free. Caries has also been associated with hypoplasia in many parts of the Third World There is no information about the chemical composition of hypoplasia enamel soothe exact reason for its greater proneness to caries is uncertain, but it is possible that its irregularity and pits may favor the development of more plaque compared with smooth well formed enamel.
In an important study of children with LEH it was found that significantly higher incidence of caries even in the posterior hypoplasia- free teeth of children whose incisors had LEH than in those who did not have this condition. Also,the incidence of caries and the enamel hypoplasia is higher in prematurely born children than in controls. Thus, evidence is strong that the factor responsible for hypoplasia of the linear type also predisposes to dental caries. Prevention of enamel hypoplasia in the Third World would portend a major reduction in caries prevalence in the affected populations.