Even with good oral hygiene, your mouth is an ideal place for bacteria to thrive. Mouthguards can not only pick up all of the bacteria from your mouth, but they can also develop some of their own if not cleaned properly. In addition to brushing and flossing your teeth before putting in a mouthguard, your mouthguard should be washed in warm soapy water and rinsed in cool water before and after every use, then allowed to air dry. (You can also brush your mouthguard as you would your teeth, with a toothbrush and toothpaste.) Your mouthguard should be kept out of reach of pets and out of extreme heat, including hot water or sunlight (heat can warp the mouthguard and change its shape, so it longer fits properly) and stored in a sturdy, vented plastic case when you are not using it.
Custom-fitted mouthguards can last several years before showing signs of wear or needing to be replaced, but stock and boil-and-bite mouthguards will need to be replaced more frequently. Children and teens will need to replace mouthguards more often to accommodate their growing teeth and mouth. To make sure your mouthguard is still fitting properly, bring it with you to your regular dental checkups. Your dentist will be able to tell you if and when you need to replace it.