Lips Lowdown

1. Brushing too hard
Using a firm-bristled toothbrush and too much pressure can permanently wear away protective enamel (triggering tooth sensitivity and cavities) and cause receding gums. Instead, use a soft brush and gentle, circular scrubbing motions for two minutes at least twice a day. When buying a toothbrush, consider that compact heads move most easily around small mouths and long, flexible handles are better than short, stiff ones for reaching back molars.

Also to consider: Going electric. Because they do the hard part for you (and do it correctly), electric toothbrushes may help you remove more plaque than manual brushes. A 1997 study published in the Journal of Clinical Dentistry showed that electric toothbrushes improved periodontal health in adults with gum problems.

2. The wrong toothpaste
Some toothpastes, especially those designated "tartar control," are too abrasive. Anything that feels gritty can erode enamel and cause receding gums. Fluoride is the only ingredient you need. Dentist-recommended toothpastes include: Mentadent ($3.29), Tom's of Maine Natural Toothpaste ($4) and Sensodyne Fresh Mint ($4.39) for sensitive teeth.

3. Forgoing floss
Bacteria on your teeth can develop into plaque, the leading cause of cavities and gum disease, in 24 hours.  Flossing once a day is essential for removing plaque.

4. Drinking lots of soda
Carbonated sodas—both diet and regular—contain phosphoric acid, which can erode teeth over a period of time. If you drink soda, use a straw to minimize contact with your teeth—and brush afterward.

5. Foods that stain
Tooth enamel is like a sponge. Anything that leaves a stain in a cup or on a plate (for example, coffee, tea, colas, marinara sauce, soy sauce, red wine) will give teeth a dull, yellowish color over time. Ask your dentist about laser whitening, bleaching or Prophy Power, a new in-office procedure in which sodium bicarbonate (a gentle whitening agent) mixes with a powerful jet of water to lift stains without removing enamel.

If you want to use a whitening toothpaste, consider that they can brighten teeth a few shades, but they tend to be harsh on the enamel.