The shape of the head allows the bristles to surround each tooth for individual cleaning. Penetrates hard to reach areas. Indicator bristles fade as a sign to replace your toothbrush head for a better clean (about every 3 months). Dentists recommend replacing your toothbrush head about every 3-4 months, or when bristles are faded and worn. Compatible with the entire lineup of Oral-B rechargeable electric toothbrush handles, except for Oral-B Sonic toothbrushes. Oral-B #1 brand used by dentists worldwide.