December 2008

Objectives To assess the transition process of sealant retention and to determine the effect of sealant loss on subsequent caries. Risk design A follow-up study from the day sealants was applied by dental nurses, every six months over a period of 30 months. Setting Mobile dental clinics at primary schools in Songkhla, Thailand. Participants 206 first grade primary school children, with 383 first permanent molars. Outcome measures Intermediate outcomes were: three categories of sealant retention: full retention, partial retention and missing sealant. The final outcome was whether occlusal caries was present or not. Results The percentages of occlusal surfaces of first permanent molars which were at risk (caries free) at time points 6, 12, 18, 24 and 30 months which became carious during the subsequent six months were 2.4, 8.00, 7.4, 5.4 and 6.1 respectively. Caries incidence was highest in the first year after sealing. Odds ratio of conversion from non-caries to caries between partial retention and missing sealant was 3.07 and between full retention and missing sealant, 0.27. Conclusion Under high caries risk and low retention rate settings, partial retention posed a high risk of caries, suggesting an urgent need to improve sealant performance. Key words: Dental caries, dental sealant, first permanent molars, mobile dental clinic, odds ratio, primary school children