Generally, tooth whitening is safe. But don’t use tooth-whitening bleaches more often than recommended. Research shows that these products wear away microscopic amounts of tooth enamel, which could increase tooth sensitivity, and even cause tooth decay.
The active ingredient in tooth-whitening bleaches is carbamide peroxide, which breaks down into hydrogen peroxide in your mouth. While studies have shown that this chemical doesn’t raise your risk for oral cancer, which was an early concern, it temporarily made teeth more sensitive for up to 78 percent of people who had their teeth lightened.
That’s because hydrogen peroxide soaks through the protective outer coating of enamel and into the softer layer of dentin underneath, irritating the nerve-rich dental pulp at the core. Microscopic cracks and leaks along dental fillings increase your odds for tooth sensitivity. And up to 40 percent of people who use those whitening trays experience temporary gum irritation as well, though it should go away in a few days.
Also remember that keeping your pearly whites pearly requires touch-ups for a prolonged effect. And if you’re pregnant or nursing, experts advise avoiding teeth whitening altogether, as the potential impact of swallowed whitening chemicals on a fetus or breast-feeding baby is not yet known.