Monica Buck
If a toothbrush’s bristles are frayed or point outward, replace the brush. (This usually occurs after three or four months of use.) “By this point, they are less effective at removing plaque, and you risk gum irritation,” says dentist Matthew Messina, a consumer adviser for the American Dental Association. If the bristles are smelly or have changed color, replace the brush right away. An electric toothbrush also wears out, so get a new head when the bristles become frayed.
Don’t rely on the blue strip. If the color fades but the bristles are straight, the brush is OK, says Messina.
If you have been very ill, replace your brush. (There is no scientific evidence that you can reinfect yourself, but $3 is a fair price for peace of mind.) Don’t bother trying to disinfect a toothbrush in the microwave or dishwasher; this will only damage the bristles.