Fissure Sealant Status, Recent Cariogenic Snack Intake, and Dental Floss Use in Relation to Permanent-Tooth Caries Experience Among Korean 12-Year-Olds: A Complex-Survey Analysis

Background/Objectives: Because restriction to dental attenders may introduce selection bias and odds ratios overstate associations for a common outcome, we analyzed the 2024 Korea National Children’s Oral Health Survey using prevalence ratios, focusing on fissure sealant status, previous-day cariogenic snack intake, and previous-week dental floss use in relation to cumulative permanent-tooth caries experience. Methods: This cross-sectional secondary analysis included 11,338 of 12,309 surveyed 12-year-olds after excluding 971 with noninformative snack-frequency responses; 103 children reporting zero toothbrushing were retained. The outcome was DMFT ≥ 1. Survey-adjusted modified Poisson regression estimated prevalence ratios using sampling weights, 26 strata, and 252 school clusters. Restricted dental-attender and alternative-outcome analyses evaluated robustness. Results: Weighted caries-experience prevalence was 60.7%, and mean DMFT was 1.94. In the multivariable model, females (adjusted prevalence ratio (aPR) 1.096; 95% CI 1.045–1.150) and children without current sealants (aPR 1.095; 95% CI 1.047–1.145) had higher caries prevalence. Once-daily versus at least twice-daily cariogenic snack intake was associated with lower prevalence (aPR 0.947; 95% CI 0.909–0.987), whereas no snack intake was imprecise (aPR 0.951; 95% CI 0.885–1.021). Floss non-use was not associated (aPR 0.999; 95% CI 0.964–1.035), and regional contrasts were non-significant in the full analytic sample. Conclusions: Sex, observed sealant presence, and one-day snack frequency were associated with cumulative caries experience, without establishing temporal sequence or a causal preventive effect. Dental floss results were inconclusive for habitual flossing and proximal caries, and regional findings were selection-sensitive. Prospective research with repeated exposure measures is warranted.