The American Dental Association recommends replacing your tooth brush about every three to four months. One method of remembering when to replace your brush is to change it at the start of each season, since it can be difficult to remember how long you have been using your current brush. However, depending on the type of brush and the brushing technique of the user, some brushes will wear out more quickly or more slowly than the 3-4 month average. Generally speaking, if the bristles on the toothbrush are in perfect condition, the toothbrush can be kept. If the bristles are worn, frayed or bent, the brush should be tossed in the trash. Bent or frayed bristles do not clean effectively and can damage the teeth and gum tissues. The other time to consider throwing a brush away is after an illness. Electric brushes such as Sonicare or Oral B power brushes should have their brush heads changed in the same manner.