Types of whitening.

Basically bleaches are used 2: hydrogen peroxide and car amide peroxide, both in varying concentrations.
The hydrogen peroxide is more potent and effective, but it is sometimes over-sensitivity in the teeth after treatment.
The first one is usually used at concentrations between 35 and 38% for conducting Whitening 1 or 2 sessions at the dental clinic. Being an agent so potent, treatment must be conducted in the clinic to monitor their impact and avoid risks, and the second is used at concentrations between 2 and 10% for one patient (at home).
The treatment is effective in the clinic, a priori, but its effect is not very durable, because the first impression clearance occurs due to dehydration of the tooth. A few days later, the tooth is re-hydrating and almost completely recovered its original state. By contrast, the patient achieves the effect more slowly, though their action may be prolonged in time for years. The most effective is to combine both treatments and apply booster dose every 2 or 3 years to maintain the result.