Do teeth whiteners really work? which is best?

I tried the one you paint on your teeth, according to directions, and I noticed no difference. I am over 40, fyi.

I have tried it all! Forget the toothpastes, strips- all OTC stuff. Go to your dentist and have custom trays made and ask for 35% Carbomide Peroxide. In about 5 minutes a day for 7 -14 days you will have white teeth. I want refrigerator white but only veneers are going to give you that color. Once you do that, the Crest strips will help maintain it. No smoking, coffee, tea or cola unless with a straw placed behind teeth! I buy my refill gel on eBay for a fraction of what dentist charges. Start slow as this is potent stuff!

I agree to use something with a high level of carbonmide peroxide level but, you have to be careful on how high you go. If you have sensitive teeth you may have extreme sense to cold and hot. Using a high level may cause gum irritation also so beware of white gums with cheap whiteners. Do not try the paint on whitener it only causes spotting. The cheapest effective way is whitestrips. You may only gain 2 shades in a few weeks but they are safe to use as the peroxide level is lower. Custom trays from your dentist is the most accurate and effectively way to whiten your teeth. Before any whitening you may want to get your teeth professionally cleaned to remove plaque which may also cause undesirable results. Good Luck!!