You can overdo anything. Even brushing your teeth. Take a stiff-bristled brush. Scrub back and forth compulsively for five minutes, as though you were trying to get tar off the sidewalk. It's possible you'll end up with "toothbrush abrasion." According to the ADA (American Dental Association), the condition is associated with factors beyond brushing: a mouth used to lots of acidic foods, citrus fruit drinks, carbonated beverages. We recommend gentle brushing, plus a toothbrush with soft, polished bristles.