This study aims to evaluate the in situ antibacterial activity of a mouthwash containing essential oils with and without alcohol on undisturbed de novo plaque-like biofilm (PL-biofilm) up to 7 h after its application.

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.

Inclusion Criteria:

Systemically healthy adults.

• Minimum of 24 permanent teeth.
• No gingivitis (Community Periodontal Index score = 0).
• No periodontitis (Community Periodontal Index score = 0).
• Absence of untreated caries.

Exclusion Criteria:

• Smoker or former smoker.
• Presence of dental prostheses.
• Presence of orthodontic devices.
• Antibiotic treatment or routine use of oral antiseptics in the previous 3 months.
• Presence of any systemic disease that could alter the production or composition of saliva.