INTRODUCTION : The purpose of this study was to compare the metabolism of Streptococcus mutans biofilms after 1 to 7 days of growth on different orthodontic adhesives. METHODS : Specimens of 6 commercial orthodontic adhesives were fabricated in custom-made molds and polymerized using an LED light-curing unit. Bioluminescent Streptococcus mutans (UA159::JM10) biofilms were grown on UV-sterilized specimens for 1, 3, 5 and 7 days (n=18/day/product) in anaerobic conditions at 37°C. The metabolism of biofilms (in terms of Relative Luminescence Units [RLU]) was measured 0, 2, 4 and 6 minutes after exposure to D-Luciferin solution using a microplate reader. A linear mixed effects model was used to analyze the logarithm of RLU (log RLU). The model included fixed effects of products, days and minutes. Tukey-Kramer post hoc tests were then performed on the significant predictors of log RLU (α=0.05; SAS software). RESULTS : Days (p