The associations between lead exposure at multiple sensitive life periods and dental caries risks in permanent teeth

Dental caries is an important public health problem in Mexico, a country also faced with high exposure to toxicants including lead (Pb).

Participants were 386 children living in Mexico City. Prenatal (trimester 1-3), early-childhood (12, 24, 36, and 48 months of age) and peri-pubertal (10-18 years of age) blood Pb levels were quantified using graphite-furnace atomic-absorption spectroscopy. Maternal patella and tibia bone Pb at 1 month postpartum were quantified with K X-ray fluorescence instrument. Dental caries presence was evaluated using decayed, missing, and filled teeth (DMFT) scores. Peri-pubertal sugar sweetened beverage (SSB) intake was estimated using a 116-item, interview-administered semi-quantitative food frequency questionnaire (FFQ). Total energy adjusted daily SSB intake was generated using the residual approach. Zero inflated negative binomial (ZINB) Poisson regression models were used to examine the associations between Pb with D₁MFT and D₄MFT at adolescence.

Maternal second and third trimester and cumulative early childhood Pb exposure were positively associated with peri-pubertal D₁MFT scores in unadjusted ZINB models (2nd trimester: RR = 1.17 (1.00, 1.37); 3rd trimester: RR = 1.20 (1.03, 1.40); early childhood: RR = 1.22 (1.02, 1.48)). These effect sizes were attenuated and no longer statistically significant after adjusting for covariates. When stratified by high/low SSB intake, a one unit increase of log-transformed 2nd trimester Pb exposure was associated with a 1.41 times (1.06, 1.86) higher D₁MFT count, and 3rd trimester Pb exposure was associated with a 1.50 times (1.18, 1.90) higher D₁MFT count among those with higher than median peri-pubertal SSB. Associations among those with lower SSB intake were roughly half those of the higher group and not statistically significant.

Pb exposure during sensitive developmental periods was not statistically significantly associated with caries risk after accounting for confounders among our cohort. However, evidence from stratified analysis suggested a Pb-caries association among children with high SSB intake.