Association of Dental Caries and Blood Lead Levels

The results showed a staggering 80% increase in the number of dental caries for every increase of 5 µg/dL (0.24 µmol/L) in a child’s blood lead level. It is also worth noting that the terms "high-" and "moderate blood lead level" are different for the three different age groups looked at, but that overall the numbers of United States children now exceeding the Australian goal for blood lead (10 µg/dL or 0.48 µmol/L) must be very small. For the worst affected age group reported in this article (2-5 year olds), nearly 75% of the children are below half the Australian goal (ie below 5 µg/dL).

Context Experiments show that dental caries rates are higher among lead-exposed animals, but this association has not been established in humans.

Objective To examine the relationship between blood lead levels and dental caries.

Design Cross-sectional survey conducted from 1988 to 1994 that included a dental examination and venipuncture blood lead assay.

Setting and Participants A total of 24,901 persons aged 2 years and older who participated in the Third National Health and Nutrition Examination Survey, which assessed the health and nutritional status of children and adults in the United States.

Main Outcome Measures For children aged 2 to 11 years, the sum of decayed and filled deciduous or primary surfaces; for persons aged 6 years and older, the sum of decayed and filled permanent surfaces; for those 12 years and older, the sum of decayed, missing, and filled surfaces.

Results The log of blood lead level was significantly associated with the number of affected surfaces for both deciduous and permanent teeth in all age groups, even after adjusting for socio-demographic characteristics, diet, and dental care. Among children aged 5 to 17 years, a 0.24 µmol/L (5 µg/dL) change in blood lead level was associated with an elevated risk of dental caries (odds ratio, 1.8; 95% confidence interval, 1.3-2.5). Differences in blood lead level explained some of the differences in caries prevalence in different income levels and regions of the United States…

Conclusions Environmental lead exposure is associated with an increased prevalence of dental caries in the US population. Findings may help explain the distribution of caries by income and region of the United States. JAMA.1999; 281:2294-2298.

[INTRODUCTION] …Several ecologic and cross-sectional studies, conducted in the 1960s and 1970s, implicated lead as a risk factor for dental caries. [7] …the most compelling basis for a causal relationship between lead exposure and dental caries showed prenatal and perinatal lead exposure to be linked to increased incidence of caries in a well-controlled animal study. [10]…

RESULTS …The population attributable risk of lead exposure is estimated to be 13.5% of dental caries among individuals exposed to …high …lead level[s] and 9.6% of caries among individuals exposed to …[moderate] …lead level[s], compared with low [lead levels] [see Table below]. …

COMMENT …Three different mechanisms can be hypothesized concerning lead exposure and dental caries: salivary gland function, enamel formation, and interference with fluoride in saliva. Watson et al [10] showed differences in salivary gland function, which suggested that exposure to lead during salivary gland development may have adversely affected the ability of the gland to produce adequate amounts of saliva.

TABLE – Blood Lead Level Distributions by Age Group, NHANES III, 1998 - 1994

Age Group years	No. of subjects	Blood Lead Level µmol/L				% With Level > 0.24 µmol/L
Age Group years	No. of subjects	Geometric Mean	Low	Moderate	High	% With Level > 0.24 µmol/L
2-5	3547	0.14	< 0.11	0.11-0.20	> 0.20	25.6
6-11	2894	0.10	< 0.08	0.08-0.14	> 0.14	12.1
> 12	18460	0.12	< 0.09	0.10-0.17	> 0.17	18.5

Saliva has several protective properties that operate against caries: it acts as a buffering agent when acids are produced, it physically removes debris from tooth surfaces, and it has immunologic and bacteriostatic properties.[23] Lead also incorporates into tooth structure before the tooth erupts into the mouth and this may result in defective enamel that is more susceptible to caries.[24] Also, lead may interfere with the bioavailability of fluoride by binding to fluoride ions in saliva and plaque, thereby reducing the preventive capacity of fluoride to remineralize enamel after an acid challenge. [25]

…In conclusion, these data suggest that blood lead levels are associated with dental caries in the US population. These data further indicate that approximately 2.7 million excess cases of dental caries in older children and adolescents may be attributable to environmental lead exposure itself or a factor that is directly linked to environmental lead exposure. If a causal association between environmental lead exposure and dental caries is substantiated, it would have important implications concerning the need to broaden the focus of health interventions for dental caries beyond modifying dietary habits, improving personal oral hygiene behaviors, and increasing fluoride exposure in high-risk groups.

Corresponding Author: Mark E. Moss, DDS, Ph.D, Department of Community and Preventive Medicine, University of Rochester Medical Center, Box 644, 601 Elmwood Ave, Rochester, NY 14642 (e-mail address)
Full article available at: http://jama.jamanetwork.com/article.aspx?articleid=190537

7. Stack MV. Curzon MEJ, Cutress TW, eds. Lead. In: Trace Elements and Dental Disease. Boston, Mass: John Wright PSG Inc; 1983:357-385.
10. Watson GE, Davis BA, Raubertas RF, Pearson SK, Bowen WH. Influence of maternal lead ingestion on caries in rat pups. Nat Med. 1997;3:1024-1025.
23. Mandel ID. Oral defenses and disease: salivary gland function. Gerodontology. 1984;3:47-54.
24. Brudevold F, Aasenden R, Srinivasian BN, Bakhos Y. Lead in enamel and saliva, dental caries and the use of enamel biopsies for measuring past exposure to lead. J Dent Res. 1977;56:1165-1171.
25. Rao GS. Dietary intake and bioavailability of fluoride. Ann Rev Nutr. 1984;4:115-136.