Knowing that the whitening gel acts on the enamel proteins, the whitening procedure is only functional on natural enamel. Therefore, the following limitations should be noted:
-By natural anatomy, the enamel is thiner near the gum. The dentin, layer of bones just under the enamel, has a tint of yellow, which is visible by transparency. It is important to understand this natural trait and to avoid whitening in vain the teeth near the gum line, irritating the adjacent gums.
-The fillings, grey or white, do not contain enamel to be whiten, therefore, their color will stay unchanged. It will be necessary to prevent the replacement after the whitening treatment if they are in the smile line.
-The crowns and porcelain bridges will not whiten, for the same reasons than the fillings.
Finally, only a minority of the population does not react to very little to the whitening treatment. The reasons of this inefficacy are still unknown. Though, experiments have proven that yellowish teeth whiten better than grey teeth.
