Genetic and environmental contributions to dental fluorosis in the primary dentition: A census-based twin study.

BACKGROUND

Although environmental exposure is the main determinant of dental fluorosis (DF), the contribution of genetic factors remains unclear. Twin studies offer an effective approach to distinguish genetic from environmental influences on this condition.

METHODS

This was a cross-sectional census-based study involving twin preschoolers aged 3 through 5 years in Teresina, Brazil. Children with complete primary dentition were included, and children who did not cooperate were excluded. The children's guardians answered questionnaires regarding socioeconomic-, health-, and zygosity-related aspects. DF was diagnosed using the Thylstrup-Fejerskov index (scale from 0 [no DF]-9 [severe DF]). Coincidence was analyzed using Spearman correlation coefficient (r) and multinomial logistic regression. Heritability (H2) was estimated using the Holzinger formula. Multilevel logistic regression identified associated factors (P < .05).

RESULTS

A total of 219 pairs of twins were included (87 monozygotic [MZ], 132 dizygotic [DZ]). The prevalence of DF was 23%. Coincidence regarding the presence of DF was considered very strong among MZ twins (rMZ = .92) and strong among DZ twins (rDZ = .76) (P < .001). Observed H2 was moderate (H2 = 66.5%). Attending a private school (odds ratio [OR], 5.17; P < .001), exclusive breastfeeding for less than 6 months (OR, 2.51; P = .015), and early-life toothbrushing with fluoridated toothpaste (OR, 1.97; P = .019) were predictors of the condition.

CONCLUSIONS

Moderate H2 and higher diagnostic coincidence among MZ twins suggest a genetic influence on the development of DF in primary dentition.

PRACTICAL IMPLICATIONS: Understanding the genetic and environmental factors associated with DF offers valuable insights for the early identification of children at risk of developing DF. This knowledge can guide clinicians and policy makers in developing targeted preventive strategies, improving fluoride management, and implementing evidence-based interventions to minimize DF and enhance pediatric oral health outcomes.