In the current study we tested the hypothesis that new 0.05% Cetylpyridinium chloride (CPC) mouthrinse formulations containing 0.12% or 0.03% chlorhexidine digluconate (CHX): 1) yield similar or better clinical results regarding the inhibition of de novo plaque growth compared to those achieved with an already marketed 0.12% CHX mouthrinse (Perio-Aid Treatment without alcohol. Dentaid, Spain), 2) reduce the side effects caused by the marketed 0.12% CHX formula and 3) that these mouthrinses have no negative microbiological effects, and they control total bacterial loads.

Inclusion Criteria:

• 18-30 years
• Good overall health without medical history or medications that could interfere with the study conduct.
• Minimum of 6 teeth per quadrant.
• Absence of probing depths ≥4mm.

Exclusion Criteria:

• Allergy to CHX or to CPC.
• Continuous use of CHX or of any other oral antiseptic in the months prior to the study.
• Any adverse medical background or long-term medications that could affect gingival conditions.
• Having taken antibiotics in the previous three months.
• Moderate to severe gingivitis (bleeding on probing ≥ 40%). 41(Van der Weijden et al. 1994).
• Pregnancy or breastfeeding.
• Smokers of more than 5 cigarettes per day.
• Orthodontic appliances.
• Fixed or removable prostheses.
• Systemic diseases that increase the risk for gingival diseases (diabetes mellitus, immunosuppression).
• Severe dental crowding.