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Dental caries examinations were carried out in an area of low caries prevalence, ascribed to a combined effect of fluoride and other trace elements. Repeat examinations in 1978 on lifelong resident children aged from 12 to 14 yr showed caries distribution patterns to be essentially the same as those found in a previous study in 1968. Some changes in DMFS scores had occurred, which were associated with changes in the strontium content of the drinking water; low caries levels were significantly associated with high strontium concentrations.

Samples of plaque and surface enamel were collected from 80 boys aged 14 years living in five communities in Ohio (USA). Mean (+/- SE) strontium concentrations in plaque were 1.43 +/- 0.18 micrograms/g (wet) and 12.34 +/- 1.63 micrograms/g (dry). For surface enamel, the mean concentration was 421 +/- 31 micrograms Sr/g. Concentrations of strontium in both plaque and enamel were significantly related to strontium levels in the drinking water. Caries prevalence as DMFS was inversely related to strontium levels in water, plaque, and enamel.

The Sr content of surface enamel of 233 teeth from nine communities was related to drinking water Sr concentrations. These water concentrations ranged from 0.02 microgram/ml to 33.9 microgram/ml. The relationship between enamel concentrations and water concentrations was linear for water concentrations less than 10 microgram/ml Sr, but leveled off at approximately 300 microgram/gm Sr in the enamel for communities with greater than 10 microgram/ml Sr in drinking water. Binding of Sr to components in the oral environment is proposed as an explanation of this effect.