Does teeth bleaching/whitening actually work?

Yes.: It's considered quite safe. Some tooth sensitivity may occur but it does go away. Ask a dentist if it's a good idea for you. Crowns and fillings do not whiten, some colors and conditions are tough, but for the average person it will whiten you teeth at least a little.

Absolutely: Works well for many, good or better for most, and not that great for a few. So much depends on the condition of the teeth and the reason they are discolored. If it is tetracycline or fluorosis staining, the results are usually limited. For normal "just older" teeth the whitening can be fantastic. Do it through your dentist and ask for the 3 minute gel (lumibrite - denmat) 32% carbamide peroxide.