Early warning system. The brand more dentists use themselves. Oral-B toothbrushes are professionally designed and incorporate features recommended by dentists. Clinical research proves that a new toothbrush can remove 30% more plaque than one three months old (1997 clinical research study). Only Oral-B has Indicator Early Warning System bristles for your teeth. The patented blue Indicator bristles are designed to fade to white, so you'll know when to change your toothbrush. Dentists recommend changing your toothbrush every 3 months.