Oral B Heads Precision Clean 2'sOverview The Oral B Precision Clean bristles reach deep between teeth and cover more surface, leaving your whole mouth cleaner than a regular manual, and power away up to 100 percent more plaque for a precise clean vs. a regular manual toothbrush. Specifications Replace your brush head every 3 months, or earlier, if the brush head becomes worn or the bristles become spread out or frayed. When bristles are worn out, cleaning effectiveness decreases.