Dental fluorosis and a polymorphism in the COL1A2 gene in Mexican children.

OBJECTIVE: To determine the allelic and genotypic frequencies of rs 412777 polymorphism in the Collagen type I alpha 2 chain (COL1A2) gene and the association with the severity of dental fluorosis in children between 6 and 12 years old in the State of San Luis Potosi, Mexico.

DESIGN: A cross-sectional study was designed; participants were 230 children from two rural communities of San Luis Potosí. Fluoride in drinking water and urine samples was quantified using a potentiometric method with a selective ion electrode. Dental fluorosis was diagnosed using the Thylstrup-Fejerskov index while the identification of the polymorphism was made by allelic discrimination, using allele-specific probes by real-time Polymerase chain reaction (PCR). Statistical analysis was carried out with Student's t-test and Chi-square and Odds Ratio (OR). A confidence interval of 95% and a value of p < 0.05 were considered.

RESULTS: The concentration of fluoride in drinking water was 2.36 ± 0.02 mg/L in Ojo Caliente and 4.56 ± 0.07 mg/L in La Reforma, the concentration of fluoride in urine was 2.05 ± 0.62 mg/L and 2.99 ± 0.99 mg/L respectively. The prevalence of dental fluorosis was 100% and the frequency of alleles was 67% wild-type and 33% mutant allelic, alleles were found in Hardy-Weinberg equilibrium (X2  = 0.33, p = 0.89). The association between the degree of dental fluorosis and the evaluated polymorphism was statistically significant (OR = 7.10, 95% CI = 3.96-12.70, p < 0.05).

CONCLUSIONS: An association of rs 412777 polymorphism in the COL1A2 gene with dental fluorosis was found. Therefore, genetic variants represent a relevant risk factor to develop dental fluorosis, as it was proven in this study conducted in Mexican children.