Early Twice-Daily Toothbrushing Linked to Reduced Risk of Adolescent Dental Caries: Study
According to a new study twice-daily toothbrushing by the age of 2–3 years was associated with a lower risk of developing dental caries during adolescence. Multiple causal inference analyses consistently estimated an absolute risk reduction of approximately 8 percentage points, corresponding to a number needed to treat (NNT) of about 13, assuming no unmeasured confounding and appropriate model specification. The protective effect was primarily observed in non-disadvantaged populations, suggesting that promoting early oral hygiene should be complemented by broader preventive strategies that address social and structural determinants of oral health.
Dental caries is a highly prevalent chronic childhood condition, yet longitudinal evidence linking early oral hygiene behaviours to long-term outcomes remains limited. This study estimated whether twice-daily toothbrushing at age 2–3 years was associated with lower incident dental caries through adolescence, under a target trial emulation framework.
Data were from the Longitudinal Study of Australian Children (LSAC) B-cohort (N = 5,107). Children with caries at or before Wave 2 (age 2–3) were excluded, yielding an incident sample of 2,970. Associations were estimated using multivariable logistic regression, propensity score matching, inverse probability of treatment weighting (IPTW), targeted maximum likelihood estimation (TMLE), and g-computation. The outcome was carer-reported dental caries. Confounders were identified via directed acyclic graph (DAG) analysis. Effect modification by area-level socioeconomic position (SEP) was assessed through a pre-specified equity analysis.
Among 2,941 children in the analytic sample, 1,559 (53.0%) developed carer-reported caries by age 14–15. Caries incidence was lower among children who brushed twice daily: 660 of 1,359 (48.6%) versus 899 of 1,582 (56.8%) in the less frequent group. The primary adjusted odds ratio (aOR) was 0.73 (95% CI: 0.63–0.85, p < 0.001). A dose-response gradient was observed (p-trend < 0.001). Effect estimates were similar across analytical approaches (OR range: 0.72–0.75). In non-disadvantaged areas, protective associations were observed (aOR = 0.65, 95% CI: 0.54–0.79). In disadvantaged areas, the association was weaker and not statistically significant (aOR = 0.91, 95% CI: 0.71–1.17; interaction p = 0.035). An exploratory falsification analysis using dental pain yielded a null result (aOR = 1.06, 95% CI: 0.91–1.23, p = 0.47), but this outcome was interpreted cautiously because dental pain may lie downstream of caries.
Twice-daily toothbrushing by age 2–3 years was associated with a lower risk of incident adolescent caries. Estimates from multiple causal inference approaches were consistent with an absolute risk reduction of approximately 8% points (NNT ≈ 13), under assumptions of no unmeasured confounding, adequate positivity, and correct model specification. Protective associations appeared concentrated in non-disadvantaged areas, suggesting that oral hygiene promotion should be combined with broader preventive strategies addressing structural determinants of oral health.
Reference:
Al-Sharani, H.M., Stormon, N., Richardson, A. et al. Early twice-daily toothbrushing and adolescent dental caries: a causal inference analysis using the Longitudinal Study of Australian Children. BMC Oral Health (2026). https://doi.org/10.1186/s12903-026-08999-9
Keywords:
Early, Twice, Daily, Toothbrushing, Linked, Reduced Risk, Adolescent, Dental, Caries, Study, Al-Sharani, H.M., Stormon, N., Richardson, A.
