What is the purpose of using mouthwash after you brush your teeth? can it be a substitute?

Fluoride: A good Fluoride mouth rinse can help strengthen teeth and may help freshen breath as part of brushing and flossing. Mouth rinses do not substitute brushing and flossing. Plaque requires mechanical removal. Anti microbial rinses can help reduce harmful bacteria in the mouth.

Mostly useless.: Most over-the-counter mouthwashes do nothing to help fight tooth decay or gum disease. Some have Fluoride in them, but it's very weak and so not real effective. Listerine is the only one proven to kill bacteria but it's effects don't last long enough to excite the dental professionals. Mechanical methods of brushing and flossing are still necessary.