Fluoridated Milk and Enamel Caries in Adolescents

The goal of this trial is to investigate whether low daily doses of fluoridated milk, in addition to oral hygiene routines with fluoridated toothpaste, can prevent caries development in adolescents' teeth. The main questions it aims to answer are: * Does fluoridated milk lower the number of caries lesions in teeth over time? * Does fluoridated milk lower the number of enamel caries lesions over time? Researchers will compare an intervention group receiving doses of fluoride in water to add to milk and a control group receiving water to add to milk. The 12-13 year participants will: * be examined at a baseline and once yearly up to 2 years * be provided directly with the doses every second month at their dental clinic * take the fluid daily