Fluoride foam and fluoride varnish are effectiveness in prevention deciduous dental caries. However, the relative clinical efficacy and cost-effectiveness of these two interventions are uncertain. This study aims to evaluate the relative clinical effectiveness and cost-effectiveness of fluoride foam and fluoride varnish in preventing dental caries in the primary teeth of preschool children with high caries risk.

This 24-month randomized clinical trial aims to compare the clinical efficacy and cost-effectiveness of topical fluoride application of fluoride foam and fluoride varnish in preventing dental caries in the primary teeth of preschool children with high caries risk in Harbin,Heilongjiang Province,China.

Preschool children (3-4 years) with high caries risk will be invited to participant in this study. An invitation letter will be sent to the parents explaining the purpose and procedures of this study.Parental concent will be sought.

The children will be randomly divided into three groups: the control group-no intervention; the intervention group 1 - applications of 1.23% fluoride foam every 6 months; the intervention group 2- applications of 2.26% fluoride varnish every 6 months.

Dental clinical examination of the children will be performed at the beginning of the study,12 months and 24 months later.The dental examiners will receive unified training and consistency test of dental caries survey.Only when the Kappa value reached 0.8 can oral examiners participate in the oral examination.Dental caries condition will be recorded. Approximately 5% of children will be re-examined to determine the reliability of the results.

The status of any possible side/adverse effects will be recorded in the follow-up examinations.

The data of the study will be analysed by SPSS Statistical Analysis Software.The differences among the groups will be calculated and compared. And p<0.05 will be considered statistically significant.

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.