If it seems like every time you go to the grocery or drug store you need go to pick up new toothbrushes for your family try this on the next new batch you buy: before using, add equal amounts of hot water and salt to a small bowl or cup. Place the brushes, bristle-side down, in  and submerge. Soak for 10-15 minutes, then rinse thoroughly. This helps the bristles to stiffen  and will prevent fraying.