Hypochlorous acid (HOCl) in a non-antibiotic antimicrobial agent used in clinical medicine. Nevertheless, its antiplaque oral effect has not been evaluated. Chlorhexidine (CHX) is the gold standard as an antiplaque agent for its high substantivity in plaque and saliva. There are no published studies evaluating the substantivity of hypochlorous acid compared to CHX. Objective: To evaluate the efficacy of mouthwashes of HOCl in substantivity evaluated by reduction of bacterial viability in saliva during 7 hours compared to CHX rinses and a placebo.