At-home tooth whitening products are generally deemed safe and effective, and you may have one in your medicine chest. So it might set your teeth on edge to read that these products minutely (if invisibly) reduce the strength of tooth enamel, according to a recent report in the American Journal of Dentistry.

Previous studies measured enamel hardness loss in microns (millionths of a meter). The new study used a nanometer scale and measured billionths of a meter. Does a billionth make a difference?

“The technique measures porousness,” says Clifford W. Whall Jr., PhD, of the American Dental Association’s (ADA) Council on Scientific Affairs. Whiteners increase porousness, but calcium and the fluoride in saliva restore the enamel within hours, Whall says, by incorporating minerals back into the tooth surface.

The problem comes when you use more than the recommended amount of bleach, slowing or disabling restoration.

“Follow the directions,” advises Kim Harms, DDS, and a consumer advisor to the ADA. Safety studies are based on product directions. “Once you venture outside those norms,” she says, “you can find yourself in uncharted waters.”

But even with proper use, problems can emerge. At-home whiteners use hydrogen peroxide or carbamide peroxide, with possible side effects including tooth sensitivity and gum irritation.

Preconditions also apply. “Treat any oral issues before you start whitening,” says Bill Dorfman, DDS, whose patients include actress Nia Long. “And the following should consult their medical doctor before treatment: pregnant or lactating mothers, those being treated for a serious illness or disorder, and children under 13.”  

The surest tooth-whitening program is steering clear of foods and drinks that discolor teeth. “Anything that can stain your carpet,” says Kim Harms, DDS, “can stain your teeth.”

Worst offenders: coffee, tea, colored soft drinks or fruit drinks, red wine, blueberries and cigarettes.

Stain reducers: If you can’t brush your teeth right after indulging in any of these offenders, Harms suggests additional maneuvers:

  • Drink through a straw to minimize the liquid’s contact with teeth.
  • Rinse your mouth with water or chew sugarless gum to stimulate saliva flow and keep the offending substance from hanging out on your teeth.