Enamel-fluoride levels in deciduous and permanent teeth of children in high, medium and low fluoride areas.

The surface enamel-fluoride concentration (approximately 4 microns) of both deciduous and permanent teeth of the central upper incisors were determined in 5-7 and 11-13-year-old children, who were born and bred in isolated areas with naturally high (3.7 parts/10(6)), medium (0.6 parts/10(6)) and low (less than 0.1 parts/10(6)) fluoride in the drinking water. Samples were taken in vivo by an acid-etch procedure and fluoride levels measured with an adapted fluoride-ion selective electrode. There were no significant differences in the fluoride concentrations or between etching depths between boys and girls, none between the contralateral incisors nor between the etching depths of deciduous and permanent teeth either in a single area or the three different ones. However, a highly-significant difference (p less than 0.01) was found in the enamel fluoride levels between the deciduous and permanent teeth in a fluoride area or among the three different fluoride areas. The ratio of the mean enamel fluoride concentration of permanent teeth to that of deciduous teeth increased with rise in fluoride in the drinking water. It is concluded that the different lengths of time, during which the crowns of deciduous and permanent incisor mineralize, contribute to this differing ratio.