Teeth whitening, also known as bleaching, is a popular cosmetic procedure designed to lighten the natural shade of teeth and remove surface stains. The process typically uses peroxide-based agents to achieve a brighter appearance. Many people have existing dental work, such as tooth-colored composite fillings, porcelain crowns, or veneers. When considering whitening, the interaction between the bleaching process and these restorations becomes a primary concern.
How Whitening Agents Interact with Dental Materials
The mechanism behind successful teeth whitening relies on the chemical reaction of peroxide agents with the organic matrix within the natural tooth structure. Carbamide peroxide or hydrogen peroxide penetrates the porous enamel and dentin layers, breaking down the large, discolored molecules into smaller, colorless ones. This chemical process is why natural teeth lighten over time.
Dental restorations are fundamentally different from natural teeth because they are made from synthetic, non-porous materials like composite resin, porcelain, or ceramics. These materials are chemically stable and lack the organic substructure that the peroxide agents can penetrate. While whitening may help remove minor surface stains that have collected on the restoration, it cannot alter the material’s original shade.
The Resulting Color Mismatch
The primary outcome of whitening teeth that have existing restorations is the creation of a noticeable color mismatch. As the natural tooth enamel lightens, the pre-existing dental work retains its original, darker color. This visual discrepancy becomes more pronounced the brighter the natural teeth become. A composite filling or porcelain crown that perfectly matched the tooth before whitening will suddenly appear too dark against the newly brightened enamel.
This effect is most problematic for restorations located on front teeth, which are highly visible when smiling or speaking. Consequently, if a patient desires a uniformly whiter smile, the existing restorations that do not match the new shade will typically need replacement. The old filling or crown must be removed and a new one fabricated using a shade that matches the final, whitened color of the natural teeth.
Strategic Planning: Whitening Before Restoration
For individuals planning both teeth whitening and new dental restorations, the correct sequence of procedures is paramount for aesthetic success. Whitening must always be completed before any new tooth-colored restorations, such as crowns, veneers, or composite fillings, are placed. This approach allows the dentist to match the new restorative material to the final, stabilized color of the natural teeth.
After the final whitening session, a waiting period is necessary before the new dental work can be finalized. This waiting period, typically ranging from two weeks to a month, allows the newly whitened tooth color to stabilize. Waiting is crucial because the bond strength of the restorative material can be negatively affected by residual peroxide, and the tooth color can slightly rebound due to temporary dehydration.
Addressing Temporary Effects and Risks
Aside from the issue of restorative materials, the whitening process itself carries common, temporary side effects. The most frequently reported effect is transient tooth sensitivity, which occurs when the peroxide agents temporarily increase the permeability of the dentin. This heightened sensitivity to hot, cold, or sweet stimuli usually subsides within a few days to a week after the treatment is completed.
Another common side effect is gingival irritation, which presents as mild redness or soreness of the gum tissue. This irritation typically results from the bleaching gel accidentally contacting the gums during the application process. Utilizing custom-fitted trays or having the procedure performed professionally with protective barriers helps minimize this soft tissue contact. Using desensitizing toothpaste before and after the whitening process can also help mitigate the discomfort.