Teeth whiteners contain acid which weakens the tooth enamel, but by using a remineralizing gel this effect can be reversed. When the unwanted colour is being removed from the teeth so are minerals and as a result the teeth become more porous.
As they become more porous they pick up stains more frequently and in some cases brown stains start appearing. Remineralizing gel contains minerals (which are in fact naturally found in our saliva but which are not usually concentrated enough to have a positive effect) which will strengthen the enamel making them whiter and glossier even without using whiteners.
If you do use whiteners then the gel is essential in order to - literally - stop the rot.
I only use the remineralizing gel myself and I have also found that it has completely stopped the problem with bleeding gums which I use to have.
If you are interested in reading more about the gel please visit my shop SILLYSCARLET , then if you have any questions please email me.