The aim of this study was to compare two visible biofilm indices in the primary dentition. The sample consisted of 90 children of both sexes, aged up to 4 years old, outpatients of the University Hospital of the Rio de Janeiro State
University. A single examiner, aided by an assistant, performed the children’s dental examination for biofilm assess-ment. A simplified visible biofilm index (BF1), which classifies biofilm as absent, thin or thick, in anterior and/or poste-rior teeth, and provides a score for the patient and not for each tooth, was compared to a conventional visible biofilm index, the visible plaque index, (BF2), which classifies biofilm as absent or present and provides scores for three sur-faces of each tooth. A statistically significant association and a strong positive correlation between BF1 and BF2 was found (Kruskal-Wallis p<0.001 / rs = 0.81 p<0.001). The time required to BF1 evaluation was approximately one third of the time required to BF2 evaluation (t test p<0.001). These results suggest that the use of a simplified visible biofilm index is feasible in the primary dentition as it showed similar findings when compared to a conventional one, besides being more practical and quicker.