The core of a tooth is dentin, a dense tissue beneath the protective outer shell of translucent enamel. While surface stains (extrinsic discoloration) affect the enamel, the overall color of the tooth is primarily determined by the shade of the underlying dentin. Dentin naturally possesses a yellowish hue, and because enamel is translucent, a darkened dentin layer makes the entire tooth appear discolored. Addressing this intrinsic dentin discoloration requires different strategies than treating simple surface stains, as the color change originates from within the tooth structure.
Understanding Intrinsic Dentin Discoloration
Intrinsic discoloration is a color change occurring within the dentin, making it significantly more challenging to remove than surface stains. Causes often involve changes to the tooth’s internal structure or the incorporation of coloring agents during tooth development.
Aging is a common cause, where the outer enamel layer gradually wears thin, allowing the yellower dentin beneath to show through more prominently. The tooth also continually produces secondary dentin, which can lead to a darker, more saturated color over time.
Trauma can lead to intrinsic discoloration, typically resulting in a gray or brownish hue as blood products from the damaged pulp infiltrate the dentin tubules. Another significant factor is the use of certain systemic medications, such as tetracycline antibiotics, during tooth formation. This drug binds to the calcium within the developing dentin, causing permanent discoloration that can range from deep yellow to gray or brown.
Teeth that have undergone root canal therapy (non-vital teeth) frequently darken over time due to the breakdown of residual pulp tissue and the accumulation of internal staining agents.
Professional Interventions for Dentin Whitening
When discoloration originates in the dentin, a dental professional employs techniques designed to penetrate the tooth structure deeply or mask the underlying color. For teeth discolored following a root canal, the specialized treatment is internal bleaching, sometimes called non-vital bleaching.
This procedure involves the “walking bleach” technique. The dentist creates a small access point in the back of the tooth and places a bleaching agent, often containing sodium perborate and sometimes hydrogen peroxide, directly into the pulp chamber. The tooth is then sealed with a temporary filling, allowing the agent to work from the inside out over several days.
For vital teeth with deep intrinsic stains, such as those caused by trauma or tetracycline, in-office deep bleaching systems are used. These treatments utilize high-concentration peroxide gels, often exceeding 35% concentration, which are carefully applied and professionally monitored. The high concentration allows the peroxide to penetrate the enamel and reach the dentin effectively, breaking down the stain molecules.
Restorative Masking Options
In cases where chemical whitening is ineffective due to severe discoloration, a dentist may recommend restorative masking options. These procedures conceal the underlying color rather than changing it. Options include bonding or the application of porcelain veneers. Veneers are thin, custom-made shells of ceramic material bonded to the front surface of the tooth, providing a permanent white appearance that completely covers the underlying dark dentin.
Efficacy of Over-the-Counter Products on Dentin
The public often turns to readily available over-the-counter (OTC) products, such as whitening strips, gels, and toothpastes, to address tooth discoloration. While these products are effective for removing superficial extrinsic stains on the enamel surface, their ability to treat deep intrinsic dentin discoloration is significantly limited.
The primary reason for this limitation is the low concentration of the active bleaching ingredients, typically hydrogen peroxide or carbamide peroxide. OTC products generally contain a peroxide concentration far lower than the professional gels used in a dental office. This restricts their ability to penetrate the enamel and reach the dentin layer, meaning any whitening effect on intrinsic stains is usually minimal and temporary.
Another factor is the method of application. Most consumer products utilize one-size-fits-all strips or trays, which lack the precise fit of custom-made dental appliances. This poor fit results in inconsistent coverage and inadequate contact time between the whitening agent and the tooth surface, further reducing the potential for deep dentin penetration.
Whitening toothpastes are the least effective for dentin discoloration. They rely primarily on abrasive agents to remove surface stains and have a minimal contact time with the tooth. While some OTC strips can promote minor color alteration, they fall short of producing the dramatic results achieved by professional, high-concentration treatments designed to target the dentin.