Here are some facts and tips in relation to teeth whitening products offered in the dentist’s clinic or in the supermarket. First, the effectiveness of the whitening agents depends on the concentration and the amount of time it gets in contact with the teeth. Therefore, the higher peroxide concentration and the longer duration of use, the greater is the whitening effect. Second, teeth whitening products only work wonders for yellow-discolored teeth, not gray teeth. However, teeth whitening reviews claim that gray-colored teeth can be whitened by bleaching products but can take a longer time period. Third, artificial add-ons on teeth like crowns and fillings are not affected by these teeth whitening products. Therefore, don’t bother trying to whiten them. Fourth, teeth sensitivity is a side effect of all teeth whitening kits. Make sure to buy recommended desensitizers to reduce this side effect while on treatment and afterwards until teeth sensitivity disappears.