The purpose of this study is to examine the effect of treatment with a lozenge containing the probiotic strain S. salivarius M18 on the formation, composition and virulence of dental plaque and in healthy orthodontic patients, compared to placebo control.

Inclusion Criteria:

1. Generally healthy males and females ≥ 10 years of age.
2. Able to read and receive a copy of the signed informed consent form.
3. Have at least 20 natural teeth.
4. Have been undergoing orthodontic treatment with fixed orthodontic appliances in the upper and/or lower jaw > 6 months.
5. An average plaque score of > 2 according to the Modified Orthodontic Plaque Index (MOPI) at the screening appointment.

Exclusion Criteria:

1. Significant oral soft tissue pathology based on a visual examination.
2. History of allergy or significant adverse events following use of oral hygiene products such as toothpastes, mouth rinses, breath mints, lozenges, or chewing gum or their ingredients.
3. History of allergies to milk proteins.
4. History of allergies towards probiotics.
5. Self-reported as pregnant or nursing.
6. Self-reported serious medical conditions.
7. Antibiotic or anti-inflammatory medication within 30 days of screening visit.
8. Acute sinusitis or severe oral-pharyngeal infections.
9. Smoker.