Most commercial teeth whiteners contain peroxide in a higher percentage than commercial hydrogen peroxide. You can whiten teeth with baking soda as a mild abrasive and use a hydrogen peroxide rinse. This method takes much longer to achieve results than the commercial whiteners, but it is less expensive, does not cause tooth sensitivity and is actually good for your gums (it helps prevent gingivitis). Brush with baking soda, then rinse with commercial hydrogen peroxide for 1 full minute. You can expect that your mouth will foam and your gums will change color temporarily. Rinse well with water afterward and then use your regular toothpaste, as the hydrogen peroxide doesn't taste good. Give this a try for a few months and you will see a difference in your gums as well as your teeth!