Teeth bleaching whitens teeth that have been darkened with age or stained by coffee, tea or tobacco. It has over a 90% success rate and can last up to five years, depending on personal habits, such as smoking or drinking coffee or tea. Results can vary in certain cases like teeth stained from smoking, taking certain medications, or fluorosis, a condition in which there is too much fluoride present. Also, bleaching will not lighten fillings or other artificial materials used in crowns, porcelain veneers, etc. Although bleaching is tough on stains but gentle on your teeth, if you have sensitive teeth, periodontal disease, teeth with worn enamel or if you’re pregnant or breast feeding, your dentist may discourage treatment.