Hydrogen peroxide is the primary active ingredient in most teeth whitening products, working chemically to lighten stains. The compound functions by oxidizing chromogens, the stain-causing molecules embedded within the tooth structure. This process breaks down the chemical bonds of discoloration, resulting in a whiter appearance. The effectiveness and safety of hydrogen peroxide are directly related to its concentration, making it crucial to determine what concentration is safe for teeth and surrounding gum tissue.
Safe Concentrations for At-Home Whitening
Over-the-counter whitening products use lower concentrations of hydrogen peroxide (3% to 10%) for unsupervised use. This range is considered safe for the general public when used according to instructions. Lower percentages, such as 6%, are often highlighted in regulatory guidelines for consumer products.
The safety of these concentrations is tied to the application time. For example, a lower percentage product (e.g., 6%) may be applied for a longer duration, such as 30 minutes daily, compared to a higher concentration product. The European Union strictly regulates consumer products, capping hydrogen peroxide content at 6% for supervised use and 0.1% for direct sales.
Carbamide peroxide is a common whitening agent used in take-home trays. It is a stable compound that slowly breaks down into hydrogen peroxide and urea, releasing about one-third of its concentration as active hydrogen peroxide. A 30% carbamide peroxide gel is roughly equivalent to a 10% hydrogen peroxide gel, providing a gentler, more gradual whitening process.
Concentrations Used in Professional Dental Settings
Professional teeth whitening treatments use significantly higher concentrations (15% up to 40% hydrogen peroxide) to achieve faster, more dramatic results. These stronger concentrations are safe only because the procedure is performed under the direct supervision of a dental professional.
The dentist employs specific safety protocols to protect the delicate soft tissues from the powerful oxidizing agent. This involves applying a gingival barrier, often a light-hardened resin, or using a rubber dam. These barriers prevent chemical burns and irritation from direct contact with high concentrations.
The treatment often involves using heat or light to accelerate the chemical reaction, limiting the time to short sessions (30 to 45 minutes). This combination allows for a rapid color change that cannot be safely achieved at home. Concentrations above 10% hydrogen peroxide should never be used unsupervised due to the high risk of soft tissue damage and extreme sensitivity.
Protecting Gums and Enamel
The primary risks associated with teeth whitening are temporary tooth sensitivity and irritation to the soft tissue of the gums (gingival inflammation). Sensitivity occurs as the peroxide penetrates the enamel and dentin, temporarily irritating the nerve within the pulp. This effect is often more pronounced with higher concentrations. This discomfort is typically mild and resolves completely within a few days after the treatment is finished.
Protecting the gums from the whitening gel is paramount, as direct contact can result in a painful chemical burn, which appears as a white patch on the tissue. At home, users can minimize gel overflow by ensuring that custom or boil-and-bite trays fit snugly against the teeth, covering the surfaces without touching the gums. Applying a thin layer of petroleum jelly or a similar barrier along the gumline before using the whitening product can also create a simple, effective shield against errant gel.
While supervised use of hydrogen peroxide is not shown to cause permanent enamel damage, chronic misuse or overuse of high-concentration gels can pose a risk to the tooth structure. Following the instructions exactly, specifically adhering to the recommended application time, is important to prevent overexposure. For managing acute sensitivity, using a desensitizing toothpaste containing ingredients like potassium nitrate before and after the whitening process can help calm the nerve and reduce discomfort.