Up to 12 hours of lasting fresh breath is based on an In-vivo study with regular use over 4 weeks. Kill the bacteria that cause bad breath with Closeup Deep Action Red Hot Gel toothpaste. Bad breath can be caused by the millions of bacteria that live in your mouth. If you dont brush and floss every day, plaque germs can form. Closeup gel toothpaste helps kill the bacteria and helps prevent bad breath.