Kindergartens Inclusion Criteria:  Kindergartens which are all located in Harbin, Heilongjiang Province, China; Kindergartens which are basically the same in terms of school scale, student source structure, economic level and sanitary conditions; Kindergartens with the same source of domestic water, or with the same fluoride concentration in water , and the fluoride concentration in water less than 1.0mg/L.  Children Inclusion Criteria:  Children aged over 3-year and under 4-year at the time of the survey; Children in good health; Children with a certain degree of understanding and good compliance; Children whose parents sign the informed consent form.  Exclusion Criteria:  Children who are unable to cooperate or have a strong vomiting reflex; Children with a history of asthma or allergies; Children with other contraindications specified in the product manual.