An appliance was designed to hold six glass disks on the buccal sides of the lower teeth, allowing PL-biofilm growth. Twenty healthy volunteers will the appliance for 48 h and then performed a mouthwash with essential oils. Disks will be removed after 30 s and at 1, 3, 5, and 7 h later. After a washout period, the same procedure will be repeated with a sterile water mouthwash and a mouthwash with essential oils without alcohol. After PL-biofilm vital staining, samples will be analyzed using a confocal laser scanning microscope analysing their bacterial viability and thickness.