| Summary: | Objectives: To test whether maternal education has a direct effect on gingival bleeding in adolescents aged 12 and to assess whether oral health behaviours over time mediate that association. Methods: Two oral health studies nested in the 1993 Pelotas (Brazil) birth cohort study were carried out in participants aged 6 (n = 359) and 12 years (n = 339). The proportion of teeth with bleeding on probing (BOP) and the median number of teeth with gingivitis at age 12 were recorded. Maternal education at birth was the exposure. Toothbrushing frequency and dental visit at ages 6 and 12 years were investigated as mediators of the association between maternal education at birth and gingival bleeding. Time-varying family income through childhood and adolescence was included as later confounder. Paternal education was taken as baseline confounder. The controlled direct effect (CDE) of maternal education at child's birth on gingival bleeding at age 12 was estimated using marginal structural models (MSM). Additionally, path analysis was employed to estimate standardized direct, indirect and total effects of maternal education at birth on gingival bleeding. Results: Adjusted analyses using MSM showed that adolescents whose mothers had <8 years of education had 3.82 higher risk of having teeth with gingival bleeding above the median (rate ratio RR 3.82; 95% CI: 1.68-8.19). Low maternal education doubled the proportion of gingival bleeding at age 12 not mediated by dental visit and toothbrushing frequency (RR 1.99; 95% CI: 1.52-2.60). Path analysis revealed that maternal education had a direct effect on gingival bleeding independently of the mediators. Conclusions: The pattern of oral health behaviours does not explain the association between mother's education and adolescent's gingival bleeding. Individual-based approaches focused on oral health-related behaviours tend to fail to prevent gingival bleeding. © 2017 The Authors. Community Dentistry and Oral Epidemiology Published by John Wiley & Sons Ltd
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