One of my back teeth has lost its enamel on its outer side. is there some way to make the tooth white? should i?

See a Dentist!: Your concern needs to be more than a cosmetic fix. Before serious damage is done, see a dentist. In recent years they have paid great attention to how the final result will look - but that will not be the first issue. Oral health is important to many other body systems. Take care of it and you'll be much better off. Best!

Broken tooth: This can be easily repaired (assuming there is no serious damage to the tooth that you are not aware of) either with a tooth colored composite filling or a ceramic crown. See a dentist to evaluate the tooth and discuss your options. Of course you should have it fixed. Your tooth is part of your oral health and the health of your entire body.

More info: When you say "lost enamel" does it mean it's broken, is it worn away and looks yellower, does it have a silver filling showing? There are many options for restoring a tooth that is cosmetically pleasing, but the tooth needs to be x-rayed and evaluated.