Many seek a brighter smile and often wonder if teeth whitening truly removes discolorations. These procedures use specific agents that interact with stains on and within the tooth structure. Understanding how these methods work clarifies their effectiveness against various types of stains.
Understanding Tooth Stains
Tooth discoloration falls into two categories: extrinsic and intrinsic stains. Extrinsic stains appear on the outer surface of the tooth enamel. They are caused by direct contact with colored substances in foods, beverages, and tobacco products. Common culprits include coffee, tea, red wine, and dark berries, which deposit pigments onto the enamel surface.
Intrinsic stains are located deeper within the tooth structure, primarily in the dentin layer beneath the enamel. Their origins vary, from genetic predispositions to certain medications like tetracycline, incorporated into the tooth during development. Trauma or the natural aging process, where enamel thins and exposes the yellowish dentin, can also lead to intrinsic discoloration. These discolorations are integrated into the tooth’s internal composition, unlike surface stains.
How Whitening Agents Address Stains
Teeth whitening relies on active ingredients like hydrogen peroxide or carbamide peroxide. When applied, these peroxide-based agents penetrate the porous outer layer of tooth enamel. Inside the enamel, these compounds undergo oxidation.
Oxidation breaks down complex, color-producing molecules, known as chromogens, into smaller, colorless components. Chromogens cause visible stains by absorbing light and creating discoloration. As these molecules break down, they reflect less light, making the tooth appear lighter and brighter. This chemical action targets the organic compounds causing discoloration without altering the tooth’s underlying structure.
What Teeth Whitening Can and Cannot Do
Teeth whitening effectively addresses most extrinsic stains. Peroxide agents break down surface discolorations caused by common dietary factors like coffee, tea, red wine, and tobacco use. Whitening treatments can lighten or remove these external pigments, restoring the tooth’s natural brightness. The success rate for extrinsic stain removal is high.
For intrinsic stains, whitening agents have limited and varied efficacy. While some intrinsic discolorations, particularly those from aging or mild trauma, may lighten, severe cases are often resistant. Stains caused by tetracycline antibiotics, for instance, are deeply embedded and typically respond poorly or not at all to conventional whitening. Similarly, fluorosis, from excessive fluoride intake during tooth development, creates white or brown mottled spots challenging to remove with whitening.
Teeth whitening agents do not affect the color of existing dental restorations. Materials like porcelain crowns, composite resin fillings, veneers, or dental bonding are not porous like natural tooth enamel. These materials do not undergo the same oxidation process as natural tooth structure when exposed to whitening gels. Consequently, if a person has restorations on their front teeth, natural teeth may lighten while restorations remain their original shade, potentially creating an uneven appearance. Patients with restorations often need to consider replacing them after whitening to match the new shade of their natural teeth.