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Sure, you rinse your toothbrush after you use it and store it upright to dry. You may even soak it in 3 percent hydrogen peroxide or Listerine mouthwash, which does significantly reduce the bacteria on it, as reported by the American Dental Association.
But you still need to replace it every three to four months — or more often if the brush frays.
Why? It harbors bacteria, usually including fecal coliform bacteria released into the air of your bathroom when you flush a toilet, according to the ADA.
Clean your toothbrush regularly and replace it at least four times a year, the ADA recommends.