Design A randomised controlled trial (RCT) was carried out over a period of 3 years. In total, 758 adolescents (age 13 years at baseline) from three areas in Sweden, from low, medium and high caries-risk areas, were recruited into the study. Bitewing radiographs were taken at baseline and at the end of the trial period by the participants’ own dentists. Radiographic caries recording was performed, blinded, by one of the authors.InterventionThree fluoride varnish regimes were employed over a 3-year period, applied as follows: twice a year at 6-month intervals (Group 1, six applications in total); three times a year all within 1 week (Group 2, nine applications in total); once a month during school terms (Group 3, 24 applications in total). All approximal surfaces were treated with a total of 0.3 ml fluoride varnish. Participants were advised to refrain from eating or toothbrushing on the day. A control group received no fluoride varnish (Group 4).Outcome measureApproximal caries prevalence after 3 years, incidence, progression and prevented fraction (PF) were measured.ResultsIntra-examiner kappa was 0.90 for all scores and 0.82 for carious surfaces. There were no significant differences in caries prevalence after 3 years between groups for dentin lesions and filled surfaces, and for enamel lesions or filled surfaces. For all areas together and in the high-risk area, however, there were significantly more dentin lesions in the control group than in fluoride varnish groups. After 3 years, statistically significant differences (P<0.001) for total caries incidence and new enamel lesions were found between test and control groups in all areas together, in high-risk areas and in medium-risk areas. The largest differences were found in the high-risk area: the control group developed 3.05±3.37 (mean±SD) lesions compared with 0.54±1.26 in Group 3, 0.95±1.67 in Group 1 and 1.4±1.89 in Group 2. Incidence was also significantly less in Group 3 than in Group 2. For all areas together, fluoride varnish treatment once a month (Group 3) had the best preventive effect with a prevented fraction of 76% compared to 57% (Group 1) and 47% (Group 2). In the medium- and high-risk areas, treatment twice a year (Group 1) resulted in a PF of 66 and 69% and was the most cost-effective option (results published elsewhere).ConclusionsMonthly fluoride varnish application was the most effective preventive regime in this school-based programme. Six-monthly fluoride varnish application was the most cost-effective method, however, for high- and medium-risk groups over the 3-year period. © 2006 EBD.
