individual samples of urine , fingernails , head-hair , saliva , plaque and enamel were collected from three groups of hungarian children , aged 14 years , who were exposed to contrasting water fluoride levels ( less than or equal to 0.11 ppm ; 0.5-1.1 ppm ; 1.6-3.1 ppm ) .
C0011389
plaque
C0016327
fluoride