Supplementary Material for: Dental caries in preschool twins: coincidences, heritability, and associated factors in a cross-sectional census-based study

Introduction: Dental caries is a sugar-dependent biofilm disease influenced by multiple factors, yet the genetic contribution to its development remains a subject of debate. Method: A cross-sectional census study was conducted with preschool children aged from three to five years old in Teresina, Brazil. Twin pairs (MZ or DZ) with complete or mixed primary dentition up to the eruption of the permanent lower incisors were included. Uncooperative children were excluded. Data were collected through questionnaires and clinical examinations using the ICDAS index. Tetrachoric correlations and multinomial logistic regression were used to assess coincidences. Multilevel Poisson regression identified associated factors (p<0.05). Results: Of the 325 eligible twin pairs, 219 (67.4%) participated in the data collection (87 MZ and 132 DZ). MZ twins exhibited a strong positive correlation for the presence of any lesion (rMZ=0.776) and a very strong positive correlation for ICDAS 4+ lesions (rMZ=0.920). DZ twins exhibited a moderate positive correlation for any lesion (rDZ=0.581) and a strong positive correlation for ICDAS 4+ lesions (rDZ=0.634). Environmental variables explained up to 50.6% of the variance in hierarchical models. Risk factors included being aged four to five years (OR=2.650; p=0.001), breastfeeding for six months or longer (OR=2.172; p=0.005), use of fluoride-free toothpaste (OR=2.444; p=0.004) and presence of hypomineralization of second primary molars (HSPM) (OR=2.198; p=0.005). Fluoridated water (OR=0.239; p=0.001) was a protective factor. Conclusion: While environmental factors play a significant role in the onset of dental caries, genetic factors may contribute to the development of the disease.