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Analysis of fingernails and urine as biomarkers of fluoride exposure from dentifrice and varnish in 4- to 7-year-old children.

Pessan JP, Pin ML, Martinhon CC, de Silva SM, Granjeiro JM, Buzalaf MA

Department of Pediatric Dentistry, Orthodontics and Public Health, Bauru School of Dentistry, University of São Paulo, Bauru, SP, Brazil.

The use of fingernails and urine as biomarkers of exposure to fluoride (F) from fluoridated dentifrice and varnish was evaluated in twenty 4- to 7-year-old children, who were divided into two groups: group A (9 caries-free children) and group B (11 children with past caries experience). They used a placebo dentifrice for 28 days, fluoridated dentifrice (1,570 ppm F) for the following 28 days, and placebo dentifrice for an additional 28 days, then returned to their usual dentifrices. Group B children also received 4-week applications of a varnish (2.26% F) while using the fluoridated dentifrice. Urinary collections were performed 24 h before the use of fluoridated dentifrice and 24 h (group A) or 48 h (group B) after. Fingernails were clipped every 2 weeks, for 26 weeks. Total F intake from diet and dentifrice was estimated. Fingernail F concentrations did not vary significantly throughout the study. Twenty-four-hour urinary F outputs (mean +/- SD, microg) were: 414 +/- 200 and 468 +/- 253 for placebo and F dentifrices, respectively (group A) and 402 +/-206, 691 +/- 345, 492 +/- 243 for placebo dentifrice, F dentifrice plus F varnish and F dentifrice, respectively (group B). The use of F dentifrice did not cause a significant increase in the urinary F output. However, when F varnish was used, a transitory increase in the urinary F output was detected (p = 0.001), returning to baseline levels in the last 24 h. Thus, F varnish is a safe method for topical F application even in children that use F dentifrice regularly. According to our protocol, urine was a suitable biomarker of exposure to F from dentifrice plus varnish, but not from dentifrice alone, while nails were not.

Published 19 August 2005 in Caries Res, 39(5): 363-70.
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