At-home teeth whitening systems can be quite effective if your teeth are in reasonably good health. As long as your tooth enamel hasn't deteriorated, your plaque and tartar is under control, and you don't have any untreated cavities, you'll (hopefully) be pleased with the results. But sometimes you don't know that your teeth aren't in such good health until your teeth whitening attempts lead to unsatisfying results—like one yellow tooth that refuses to whiten. 

Chemical Reaction

Whether you use a whitening gel and applicator trays, whitening strips, or a whitening pen, the chemical reaction that whitens dental enamel remains the same. The active ingredient (hydrogen peroxide) is absorbed into the surfaces of your teeth, and these surface layers are made of dental enamel. This action reduces the concentration of the pigmented molecules visible in your surface dental enamel, essentially bleaching away discoloration. It's a simple process, but its effects on dental enamel can be striking. Its effects on dental dentin will be minimal.

Tooth Structure

The surfaces of your teeth are made of dental enamel. It protects the rest of the tooth's structure, which is mostly made of dentin. Enamel will respond favorably to teeth whitening. Dentin will not. When enamel has corroded (often a precursor to cavities and decay), it will expose the dentin beneath. This dentin will not whiten the way enamel will. When key teeth remain stubbornly yellow after your at-home whitening treatments, these teeth may have thin or otherwise deteriorated enamel.

Enamel and Dentin

Repeated attempts to whiten teeth with deficient enamel won't yield the desired results. It's not about the amount of the whitening product or the frequency of your sessions. If anything, the corrosive effects of whitening gel will irritate your teeth. Remember, this hydrogen peroxide is compatible with dental enamel but not so much with dentin. To complete the whitening process, see your dentist.

At the Dental Clinic

The teeth with questionable enamel will be inspected. Your dentist may need to manually replace your deteriorated dental enamel (which can't be regrown naturally). This can most easily be achieved with dental bonding, which is when a thin coat of tooth-colored dental resin is spread over the tooth, creating a new protective outer layer and concealing the tooth's discoloration. This resin will match your other (whitened) teeth. Other treatment options are possible, such as applying an appropriately-colored porcelain veneer to the outward-facing surface of the tooth.

So if one (or more) of your teeth remains stubbornly yellow after your whitening attempts, see your dentist. You're probably going to need some help to complete your whitening journey.

Contact your dentist to learn more about teeth whitening and other cosmetic dental procedures.