Nearly half of the 12-year-old children in China have dental caries (tooth decay) and most of the lesions are in the fissures of the first permanent molars. This study aims to investigate the effectiveness of three methods in preventing fissure caries in permanent teeth in Chinese children, namely resin fissure sealant, sodium fluoride varnish, and silver diamine fluoride solution. The cost-effectiveness of these methods will also be compared. About 400 children, aged 8 to 9 years, will be recruited. Clinical examination of the children will be conducted in school using portable dental lights and instruments to identify teeth that need caries prevention. The children will be randomly allocated to one of the three test or the control groups. Treatments will be provided in the study primary schools according to standard clinical protocols. Follow-up examinations will be carried out every six months for 30 months to assess whether the preventive methods are successful, i.e. no dental caries develops in the treated teeth. The findings of this study will be of great value to dentists and public health authorities in deciding on the most appropriate dental caries prevention programme for school children in China and other developing countries.

Inclusion Criteria:

• school children in good general health
• have at least one permanent first molars that has deep occlusal fissures, or fissures with signs of early caries

Exclusion Criteria:

• children with major systemic disease or taking long-term medications
• not cooperative or refuse dental treatments