Supplementary Material for: Effects of a 2-year early childhood vitamin D3 intervention on tooth enamel and oral health at age 6-7 years

Introduction: The aim of the study was to compare the effects of a 30 µg/day vs 10 µg/day vitamin D supplementation, given during the two first years of life, on oral health at the age of six to seven years. Methods: In 2013-2016, we conducted a randomized, double-blinded, clinical trial from age 2 weeks to 2 years of daily vitamin D3 supplementation (10 vs 30 µg), including 975 healthy infants. For the present follow-up study at age 6-7 years, a sample of 123 children underwent oral examination by investigators blinded to the intervention group. Tooth enamel defect and caries findings, oral rinse active matrix metalloproteinase-8 levels, and tooth eruption were recorded. The intervention groups were compared with chi-square and Mann Whitney U tests. Associations of the oral health outcomes were evaluated with correlation analysis and logistic regression. Results: Of the children (median age 7.4 years, 51% boys), 56% belonged to the 30 µg intervention group. Developmental defect of enamel (DDE) was found in 39% of the children in the 10 µg intervention group and in 53% of the 30 µg group (p = 0.104). In total, 94% of children were vitamin D sufficient (25(OH)D ≥50 nmol/l) and 88% had caries-free teeth. No associations were found between vitamin D intervention group in infancy and oral health or the presence of DDE. Conclusion: Daily supplementation with 10 µg vitamin D3 in the Northern Hemisphere seems adequate in healthy children younger than 2 years in ensuring good oral health at early school age. Trial registration: ClinicalTrials.gov (NCT04302987)