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The uptake of alkali soluble and alkali insoluble fluoride on and in fluorotic enamel was investigated in vitro. Teeth from Kenya, assigned score 3 in accordance with Thylstrup-Fejerskov's fluorosis index, were used. The enamel was treated with either a neutral 2% NaF solution, a 0.2% NaF solution (pH 5.5), or the supernatant from a 0.1% NaF-containing toothpaste (pH 7). The treatment time was 1 h. The reaction product formed on the enamel was analyzed by KOH extraction and acid etching. Significantly higher amounts of alkali soluble fluoride were formed on the enamel from the 2% and 0.2% NaF solutions, as compared with the control. There was also a significant increase in the firmly bound fluoride after treatment with the neutral 2% NaF solution.

The present longitudinal study was conducted on ten children from age 5-6 years to determine the post-eruptive enamel changes of fluorosed permanent incisors. The children were born and reared in an area of Kenya with a water fluoride level of 14-45 parts per million. The incisors were examined and photographed periodically from the time of eruption over a period of 2 1/2 years. It was noted that the fluorosed incisor was intact as it erupted and then it underwent a variety of changes. In some there was mechanical breakdown (pitting) of the chalky white enamel which occurred rapidly initially and then the breakdown slowed down by 2 years. In others, there was smoothening of the pitted enamel resulting in a translucent appearance. Alternatively there was some degree of patchy staining of the enamel without surface breakdown. Much of the cervical 1/3 of the enamel remained intact even in teeth with severe breakdown. In most cases, these changes were bilaterally symmetrical. The possible reasons for these changes are discussed.