Blood lead level and dental caries in school-age children

Environmental Health Perspectives, Oct, 2002 by Allison Gemmel, Mary Tavares, Susan Alperin, Jennifer Soncini, David Daniel, Julie Dunn, Sybil Crawford, Norman Braveman, Thomas W. Clarkson, Sonja McKinlay, David C. Bellinger

Blood lead levels were generally low, with an overall mean of 2.3 [micro]g/dL (SD, 1.7), although it was significantly higher in the urban than in the rural subgroup (p < 0.0001). The maximum blood lead levels were 13 and 7 [micro]g/dL in the urban and rural subgroups, respectively. The lead exposure of this study sample was comparable with that of the general population: In the most recent NHANES survey, the mean blood lead level of 6-11 year olds was 2.5 [micro]g/dL (95% confidence interval: 2.2-2.7; Brody et al. 1994).

In the complete cohort, InBPb and InDFS were marginally positively associated (p = 0.06). Because the InBPb x InDFS interaction term was statistically significant (p = 0.001), however, further analyses were stratified by geographic site. In the urban subgroup, InDFS and InBPb were positively associated (p = 0.02). In the rural subgroup, the slope of the relationship was negative, although not significant (p = 0.12). Figure 1 shows the mean values for the total number of carious surfaces for children with blood lead levels of 1, 2, 3, and [greater than or equal to] 4 [micro]g/dL, by site. In the urban subgroup, children with blood lead levels of [greater than or equal to] 4 [micro]g/dL had, on average, two more carious surfaces than did children with a blood lead level of 1 [micro]g/dL, an increase of approximately 20%.

In simultaneous multiple regression analyses adjusting for age, sex, family income, ethnicity (urban subgroup only), education of a child's female guardian, maternal smoking, frequency of a child tooth brushing, the firmness of the toothbrush bristles, and the frequency of gum chewing, the positive association between InBPb and InDFS in the urban subgroup remained significant (p = 0.005; Table 2). The only other significant predictor of InDFS in this subgroup was ethnicity, with children in the black group having fewer carious surfaces than did children in the other/mixed group. In the rural subgroup, the negative association between InBPb and InDFS, adjusted for covariates, was not significant (p = 0.09). Among this subgroup, InDFS was inversely related to child age (p = 0.03), and children of mothers with a high school education had more carious surfaces than did children of mothers with at least some college (p = 0.01).

To determine whether the association between blood lead and caries prevalence is similar for primary and permanent teeth, the full regression model was refitted, stratifying the analyses by site (urban, rural) and tooth type (primary, Table 3; permanent, Table 4). Among children in the urban subgroup, InBPb and InDFS were positively associated in primary teeth (p = 0.002) but not in permanent teeth (p = 0.8). Among children in the rural subgroup, InBPb and InDFS were not significantly associated in either primary teeth (p = 0.1) or permanent teeth (p = 0.3). In both subgroups, age was inversely associated with InDFS in primary teeth (p = 0.0003 in the urban subgroup, p = 0.0001 in the rural subgroup) and positively associated with InDFS in permanent teeth (p = 0.0001 in both urban and rural subgroups). For primary teeth, InDFS was lower among children in the black category than among children in the other/mixed category in the urban subgroup (p = 0.009). In the rural subgroup, children of mothers with a high school education had significantly higher InDFS than did children of mothers with greater education (p = 0.0003). In the rural subgroup, InDFS in permanent teeth was inversely associated with age (p = 0.05) and with use of medium/hard bristles compared with soft bristles (p = 0.04).