Mouthwash is not particularly necessary and not all mouthwashes are useful. Mouthwashes containing Listerine our chlorine dioxide are very helpful because they help to kill and maintain the bacteria in your mouth. It can help maintain good breath as well as help maintain strong teeth. Mouthwash cannot do all the work but if your are already brushing, flossing, visiting the dentist and eating well, mouthwash is the cherry on top that will make your dental health great.