Purpose: To determine whether family income, age and educational level of the mother of the family are associated with self-reported use of dental floss over a 13-year period in a city in southern Brazil. Materials and Methods: A comparison of two household surveys was carried out where mothers of the family were interviewed using a structured questionnaire in order to obtain demographic, behavioural and socioeconomic information. In total, 852 and 984 households were included in 1996 and 2009, respectively. Self-reported use of dental floss was assessed dichotomously (yes/no). Poisson regression models were fitted to study the association between sociodemographic variables with the use of dental floss. Proportion ratios (PR) and 95% confidence intervals (95% CI) were reported. Results: The proportion of dental floss use increased from 48% to 59% over 13 years. The probability of dental floss use increased 1.23 times from 1996 to 2009 (PR = 1.23; 95% CI 1.13-1.34). Households with mothers ≥50 years old presented a 28% lower probability of using dental floss than households with mothers ≤35 years old. In households with higher family income and higher educational level of the mother, probabilities of flossing were 90% and 97% higher. Conclusion: Family income, age and educational level of the mother of the family are associated with self-reported use of dental floss over 13 years. Keywords: dental floss, oral hygiene, risk factor