Why me? Some of us are genetically programmed for pearly whites, but others inherit teeth tinged with yellow or brown. And coffee, tea, red wine, colas, and tobacco can take a toll. Another culprit is the antibiotic tetracycline-no longer prescribed to kids, since it can stain developing teeth. Aging and tooth trauma also can cause dullness and discoloration. Battle plan: if you drink coffee, chase it with water and then brush, says N.Y.C. cosmetic dentist Jan Linhart. This will help wash away stains before they penetrate the enamel. Whitening toothpastes fight surface stains, "but they don't actually change the color of the tooth enamel," says Linhart. Bleaching gets at stains inside and out, because the solution travels through tubules inside the teeth. If you want to try home bleaching, use a kit that contains hydrogen peroxide (Crest Whitestrips, $40; at drugstores) or carbamide peroxide (Rembrandt Dazzling White).