Subjects This study was a secondary analysis of data from a 2-year cluster randomized trial that tested an oral preventive program among 30 Aboriginal communities in Australia's Northern Territory between 2006 and 2008. Thirty consenting communities were allocated to either an intervention group (n = 15, oral health promotion and FV) or control group (n = 15, no intervention). The average cluster size was 23 children, with a range of 4 to 71 children per cluster. The surface-specific data were collected from the baseline and follow-up examinations of 543 three-to five-year-old children (274 boys and 269 girls). Children's median age at the 2-year follow-up was 58 months (range 42-71 months). At baseline the mean number of decayed-missing-filled surfaces (dmfs) (95% CI) was 4.6 (3.9-5.2) for the control group and 4.9 (4.2-5.6) for the intervention group. 1 Nearly two-thirds of the children had some caries experience at the baseline examination, and almost all caries was untreated. At the follow-up examination, 94% of the children (510/543) had caries experience, and most of the caries was untreated. Key Exposure/Study Factor Between May 2006 and December 2008, teams of 2 to 4 study personnel made five visits to each of the 15 intervention communities at 6-month intervals. Interventions included Duraphat fluoride varnish (FV) applications every 6 months for 2 years, oral hygiene education to parents, and other community-based activities to promote oral health. Control communities (n = 15) were visited only twice, for clinical examinations at baseline and 2 years later. Main Outcome Measure This secondary analysis focused on caries increment or conditions of specific tooth surfaces of the primary dentition. There were 543 children with clinical data from both baseline and 2-year follow-up examinations. At each exam, each tooth surface (up to 100 per child) was classified according to the most severe condition diagnosed: sound surface, opacity, hypoplastic enamel loss, precavitated lesion (d(1)), cavitated lesion (d(3)), restoration, extracted, or missing and unavailable. Additional information collected included children's gender and age and community water fluoride level. Transition from sound, opaque, hypoplastic, or precavitated status to decayed, filled, arrested, or extracted was recorded as (crude) caries increment, whereas the inverse biologically implausible transition was classified as a caries decrement. To correct 'examiner reversals', a 'net' caries risk (2-year cumulative incidence) was computed by subtracting reversals from the crude increment. Main Results Based on the surface-level measurements, the risk of caries in the FV group relative to the control group was 0.79 (95% CI = 0.74-0.84), equivalent to a 21% reduction in caries incidence. After adjustment for community water fluoridation, the estimated relative risk (RR) was 0.75 (95% CI = 0.71-0.80), equivalent to a 25% reduction in caries incidence. The overall surface-level 2-year caries risk was 10.7% for the control group and 8.2% for the intervention group. Sound surfaces received slightly more benefit (RR = 0.73; 95% CI = 0.69-0.79) compared to opaque surfaces (RR = 0.77; 95% CI = 0.65-0.92) but there were almost no differences for precavitated or hypoplastic surfaces. When tooth anatomy was considered, posterior teeth and pits and fissures received slightly more benefit (RR = 0.72; 95% CI = 0.64-0.80) compared to maxillary anterior facial surfaces (RR = 0.77; 95% CI = 0.71-0.83). Among sound surfaces at baseline (79% of all surfaces), maxillary anterior facial surfaces received the most benefit (RR = 0.62; 95% CI = 0.49-0.77) and pits and fissures the least (RR = 0.78; 95% CI = 0.67-0.90), Z homogeneity = 1.67, p = 0.05. For this analysis, the surface-level interexaminer reliability estimate, the unweighted kappa statistic was 0.50 (95% CI = 0.41-0.59), indicating moderate agreement between the gold-standard examiner and the study examiner. Conclusions The authors conclude that a community intervention including twice-a-year FV applications among Australian Aboriginal preschool children reduced the surface-level 2-year caries risk by 25%. Results also indicate that sound surfaces received the greatest relative benefit from FV applications. Based on these findings, authors suggest that net caries-preventive benefit would be maximized by assigning greatest priority during FV application to surfaces that appear sound rather than surfaces that have visible loss of enamel (classified here as hypoplastic or precavitated). Efficacy was relatively homogeneous across different tooth types; however, among sound surfaces, maxillary anterior facial surfaces received the greatest caries-preventive benefit.
