text: if me use whitening, what the effect? usefull or harmful??? for teeth whitening you really ned to see your dentist for the best results and for the proper care.  whitening toothpastes will not change the shade of your teeth.... at best, they may do a little better at removing some of the everyday stains caused by such things as smoking and drinking dark beverages. i do not recommend them because they are very abrasive and could potentially harm the enamel of the teeth. as for the over-the-counter bleaching materials such as crest white strips, none of them are approved by the ada (american dental association). for products that are approved by the ada you will need to see your dentist. also, it's best to be under the care of a dentist while you are whitening due to high reports of sensitivity and in case of any allergic reactions.