Inclusion Criteria:  Male or female adult patients with age range 18-30 years old. Good to fair oral hygiene indicated by healthy non-inflamed gingiva and absence of carious lesions at the time of recruitment. Full permanent dentition (except third molars). Mild to moderate crowding. Lack of using any mouth rinse for at least 1 month before the initiation of the study, and revealing no sign of sensitivity to mouthwashes.  Exclusion Criteria:  Presence of any systemic or infectious diseases. History of antibiotic or hormonal therapy within the past 6 months prior to orthodontic treatment. History of smoking. History of professional cleaning (scaling) within the past 3 days prior to sample collection. Presence of major untreated dental conditions such as untreated carious lesions at baseline.