Background Dental caries is the most prevalent disease worldwide. The objective of this study was to determine the mean of decayed/missing/filled in permanent teeth (DMF-T index) and in primary teeth (dmf-t index) and verify the association with oral health behaviours and socio-demographic factors in children aged 5–12 years old.

Participants and methods A sample of 605 children aged 5–12 years old, attending twenty-seven public schools in Sátão, Portugal, was enrolled in this cross-sectional study. Clinical examinations of oral health status were carried out according to WHO criteria to determine the prevalence of dental caries and the DMF-T and dmf-t. Structured questionnaires for interviewing children on oral health behaviours and socio-demographic factors were used.

Results Prevalence of dental caries is 72.1%. Dental caries experience was 0.93 DMF-T and 2.99 dmf-t, higher among the female sex (3.04 vs 2.93; p=0.02). The total DMF index was associated with residence area (rural=4.18 vs urban=3.43; p<0.01), parents' level of education (0–4 years=4.29; 5–6 years=4.15; 7–12 years=3.69; >12 years=1.73; p<0.01) and dental appointments in the last twelve months (no=4.24 vs yes=3.33; p<0.01).

Conclusions We found a high prevalence of dental caries in primary and permanent teeth, associated with socio-demographic factors. Oral health programmes and primary preventive strategies should be considered.