Several factors can affect whitening results either immediately or overtime. One is that the tooth whitening effect is lost as stain molecules that are initially broken up by the whitening process come back together over time. Researchers also believe that dehydration of the tooth enamel during the whitening process provides a temporary whitening effect and then once the enamel rehydrates, that effect is lost.
Other factors that can affect whitening results include:
1. Concentration and type of bleaching agent.
Teeth whitening products purchased over-the-counter have lower amounts of peroxide-based whitening agents than the products used in a dental office. Dental office gels contain 30 to 35 percent peroxide. At-home whitening gels have around 10 percent. Toothpaste, pens, rinses have about a 3 percent concentration.
Natural whiteners such as baking soda, table salt, vitamin C and bamboo powder will also whiten at different rates than peroxides.
The different amounts, strengths, and types of whitening agents mean that each product needs to be used for different lengths of time to achieve a particular level of whitening. A do-it-yourself whitening product is meant to be used over the course of a few days or weeks before results are visible. Treatments done in the dentist’s chair are designed to work quickly with the help of a gel-accelerating light.
2. Method of application.
Whitening toothpaste, mouthwashes, pens, trays and gels, strips all have different ways that they address tooth stains. Toothpaste and mouthwashes only come into contact with tooth surfaces very briefly compared to pens, gels, and strips, and so need to be used for longer periods of time.
Certain medications and root canal infections and treatments can also cause greyish internal stains that can take months to achieve even minor results with on-the-surface tooth whiteners. In such cases, usually, only internal bleaching by a dentist will have any effect.
3. Following treatment instructions.
Successful results depend on patients following the instructions on the package or given by their dentist when using products or continuing treatment at home. These instructions may not only refer to how to use the product, but also to what not to do at home to keep teeth white. For example, it is recommended that people stay away from drinking tea or coffee or red wine in the first few days following whitening treatment; however, not everyone follows those instructions.
4. Lifestyle habits.
Whitening treatments won’t be as effective if people continue to eat and drink pigmented foods or continue to take certain medications such as those containing tetracycline or doxycycline. Such teeth-staining habits include: drinking excessive amounts of coffee, tea, colas, red wines, acidic foods (eg: tomatoes, oranges), smoking. For many people, it’s these kinds of habits that caused the staining in the first place; so, continuing them afterward will only cause the stains again. The good side is, these kinds of stains tend to be more yellow than grey which usually responds better to whitening agents.
5. Tooth surface.
Bleaching agents will only work on natural tooth materials, not on veneers, caps (crowns), bridges, porcelain or bonding. Thicker enamel or calcium deposits will also affect results. It is easier for the gel to penetrate thinner tooth surfaces. Calcium deposits will actually grow whiter with tooth whitening treatments but will fade a few days after whitening.
6. Stage of tooth eruption.
Teeth whitening is usually reserved for people with all adult teeth are properly in place. If teeth are whitened while they’re still coming in, there will be a difference in color between the crown and the portion of the tooth that came up after the whitening was done. This is why people below 16 years of age may not be good candidates for whitening treatment.