Whitening is not recommended or will be less successful in the following circumstances:

Sensitive teeth and allergies. Persons with sensitive teeth and gums, receding gums and defective restorations should consult with their dentist before using a tooth whitening system. If you are allergic to peroxide (the whitening agent) you should not use a bleaching product as well.

Age and pregnancy issues.  Teeth whitening is not suggested in children under the age of 16. This is for the reason that the pulp chamber, or nerve of the tooth, is enlarged until this age. Bleaching under this condition could irritate the pulp or cause it to become sensitive. Also teeth whitening is not suggested in pregnant or lactating women.

Gum disease, worn enamel, cavities and exposed roots. Those who have gum disease or teeth with worn enamel are commonly dissuaded from undergoing a tooth whitening procedure. Before undertaking any whitening procedure, cavities need to be treated. It happens for the reason that the whitening solutions go in into any existing decay and the inner areas of the tooth, which can cause sensitivity. In addition, whitening procedures will not work on exposed tooth roots as roots do not have an enamel layer.

  Darkly stained teeth. Yellowish teeth react well to bleaching, brownish-colored teeth respond less well and grayish-hue or purple-stained teeth may not respond to bleaching at all. Blue-gray staining caused by tetracycline is more difficult to lighten and may necessitate up to 6 months of home treatments or several in-office appointments to successfully lighten. Dark-stained teeth may be better candidates for another lightening alternative, for example veneers, bonding, or crowns. Your dentist can discuss the options best suited for you.

Fillings, crowns and other restorations. Tooth-colored fillings and resin composite materials used in dental restorations such as crowns, veneers, bonding, and bridges do not whiten. Consequently, using a whitening agent on teeth that contain restorations will results in uneven whitening-in this case, making the teeth without restorations appear lighter than those with restorations. If you consider some whitening procedure, it should be done earlier than the placement of restorations. Persons with numerous restorations that would cause uneven whitening may be better off considering bonding, veneers or crowns rather than a tooth whitening system. Inquire your dentist what strategy is best for you.

Unrealistic expectations. Those who expect their teeth to be a new "blinding white" may be disappointed with their results. Smokers need to understand that their results will be partial if not avoiding continued smoking, especially during the bleaching process. A healthy guide as to a reasonable degree of whiteness to achieve with a whitening process that would give a natural appearance to a person's teeth is a somewhat whiter color than the whites of your eyes.