Frequently Asked Questions on Teeth Whitening

While it is true that teeth whitening by bleaching does work, it does not come without side effects. There are many reported incidents of increased tooth sensitivity after bleaching. Prolonged exposure to bleaching agents can damage tooth enamel. If the treatment is not administered properly, there can be complications like gum irritation. The oxidizing agents are very strong and can damage the soft tissues of your mouth. The bleaching effect can cause some irritation and increased sensitivity to cold and hot fluids and sometimes even to air. In the case of home bleaching, there is a chance that some of the bleaching gel might be ingested by patients. In such a case, the person might experience burning or nausea.

According to a Brazilian study done in 2004, increased sensitivity is commonly an inherent characteristic of the bleaching process. During bleaching with carbamide peroxide, the bleaching agent actually causes a dissolution of isolated groups of enamel rod prisms. The dissolution of the individual enamel rod prisms is so thorough that the dentin actually becomes exposed microscopially. In turn, cold water that subsequently travels down the evacuated spaces causes a slight contraction of the now exposed odontoblastic process. This in turn causes sensitivity. It actually will continue until the temperature of the tooth warms back to body temperature.

The photomicrograph above shows various photos of enamel taken during a teeth whitening treatment using carbamide bleaching agents. A greater degree of porosity (enamel prism dissolution) occurs as the bleaching time is increased. The complete dissolution of the enamel rod prism could account for sensitivity to cold water after bleaching.

When receiving professional teeth whitening, minimal sensitivity and good whitening results rely on factors such as pH, viscosity, stability and, most importantly, the rate at which the carbamide breaks down into hydrogen peroxide and then oxygen. Carbamide has been chosen by many manufacturers as it is more stable than hydrogen peroxide. However, this also causes a slower release of the oxidizing agent and necessitates longer procedures. Some manufacturers have tried to accelerate this by adding heat (in the form of light). This can have a minimal effect but it can also be a major cause of extreme sensitivity.

We have written an in-depth article on possible teeth whitening dangers located in the article section.