Many factors work to destroy the naturally white smile you were born with. Tobacco, certain foods, and certain drinks actually stain teeth. These substances continually work on our teeth causing our white smile to gradually fade. Hot coffee and tea are especially hazardous to your smile because they change the temperature of teeth. This temperature change - hot and cold cycling - causes the teeth to expand and contract allowing stains to penetrate the teeth. Cutting down on coffee and tea can go a long way to creating a great smile. Foods that are slightly acidic are also dangerous to your white smile. These foods open up the pores of the tooth enamel allowing stains to move more easily into the tooth.
Your dentist can help you with more tips on keeping a white smile.