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NIH: Consensus Development Conference on Diagnosis and Management of Dental Caries Throughout Life: Background

NIH organized conference that produced consensus statements on important and controversial topics in medicine and dentistry.

Exposure to Metal Ions and Susceptibility to Dental Caries

William H. Bowen, B.D.S., Ph.D.:

There are large unexplained disparities in the prevalence of dental caries from one region of the United States to another. Disparities in the levels of caries that have not been explained by conventional hypotheses are found within states, counties, and cities. The highest prevalence of dental caries in children is found in the northeastern part of the United States and in the inner cities. Coincidentally, those are also the areas where the highest exposures to lead occur.

There are good theoretical reasons for believing that exposure to lead during and possibly after tooth formation may enhance susceptibility to dental caries. Lead in its atomic structure resembles calcium and may replace calcium in the bones and teeth of young people, thus altering their solubility and other properties. Furthermore, lead may combine with fluoride to form lead fluoride, which is virtually insoluble. It is also well recognized that exposure to lead during fetal development may affect the maturation of infants� sympathetic and parasympathetic innervation, which have been shown to affect the development of salivary glands. Reduced salivary flow enhances susceptibility to dental caries.

Lead and Disease

Lead is one of the most toxic and pervasive pollutants in our society. High levels of lead in the blood are the most prevalent environmental threat to the health of children in the United States (Healthy People 2000). The Centers for Disease Control has lowered the acceptable concentration of lead in the blood in young children from < 25 to < 10 ug/dL. Despite the documenting of lead�s danger to health, however, little information has been obtained on the toxicity of lead to oral health. Nevertheless, the preponderance of existing epidemiological data show an adverse relationship between lead in the environment and the prevalence of dental caries. Furthermore, all the available data show that lead may disrupt the formation of enamel and dentin. The results of studies conducted with rats also illustrate the potential for lead to affect salivary gland function adversely. We have identified seven clinical studies between 1969 and 1999 that showed a positive correlation between elevated levels of lead in soil, drinking water, and tooth enamel, and prevalence of dental caries. One study showed no correlation between levels of lead in enamel and the prevalence of caries. Two studies using rats showed a positive relationship between prenatal and perinatal exposure to lead, levels of lead in enamel, and incidence of dental caries. On the other hand, numerous studies have failed to show a relationship between postnatal exposure to lead and caries experience in rats.

We did not find any literature on studies exploring the effect of lead on salivary gland function in humans. Results from three studies conducted with rats, however, show very clearly that exposure prenatal or postnatally may reduce stimulated salivary flow. The effects on resting flow were not explored.

Although the clinical studies mentioned above may have flaws, the relationship between lead exposure and caries is consistent. Results from humans and animals show that enamel accumulates lead, and that enamel formation can be adversely affected.

Many states now require that the blood levels of lead in infants be determined and recorded. If it is agreed that exposure to lead constitutes a risk for dental caries, the blood lead levels of children should be part of their dental record. This information could form the basis for preventive measures and alert the dental practitioner to behavioral and other problems associated with lead intoxication.

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