If they darken more than you want, you can bleach them again. As long as you save your models and bleaching trays, you can do a touch up bleaching for a few days at any time in the future by purchasing an inexpensive touch-up kit of bleach material.

Some people simply start out with darker teeth than other people. Anything that could stain a white cloth can cause your teeth to darken. The worst offenders are smoking of any kind, dark beverages like red wine and cokes, and dark gravies and sauces. Skipping regular cleanings also lets deposits build up and penetrate into the tooth to darken them.

Regardless of your habits, you can have whiter teeth. If your teeth are dark and your habits tend to stain your teeth, you will get a less than desirable result from the tooth bleaching and will have to do it longer and more frequently. You do have other options, such as porcelain veneers, that can give you the color you want without relying on tooth bleaching.

You can always start with bleaching and then use veneers later. In your consultation with the doctors, they will let you know what results you can expect from bleaching and then you can decide what you want to do. Some people may decide to start with bleaching and contouring and then do veneers in the future.