The aim of this study; The aim of this study is to investigate the biofilm uptake in transparent plaques, which are widely used today, and the effect of 5% Lugol on both biofilm formation (inhibition) and eradication of the formed biofilm. 3 different clear aligners were cut into 5mm rounds (n=10) and S. mutans biofilm formation on them was examined by both colony counting method and SEM. The effect of 5% Lugol was determined as MIC. Inhibition at sub-MIC values and MIC -2 MIC values were tested. Kruskal Wallis analysis of variance (ANOVA) and analysis of variance in repeated measures were used to evaluate the data. When the data obtained with colony forming unit count (cfu) and SEM images were compared, biofilm formation was observed at the end of the 3rd hour in all 3 plates and reached the maximum at the end of 48 hours. 5% Lugol provided complete inhibition in all 3 plaques, but although it was effective in eradication, it could not completely remove it. When 5% Lugol was applied without biofilm formation, it prevented the biofilm formation regardless of the transparent plaque brand, but it was able to partially remove the formed S. mutans biofilms.