We'd all love to have brilliant white smiles where our teeth look amazing... but the fear of what happened to Ross' teeth on that one episode of Friends always looms large.

(Here's hoping your crush doesn't have a black light in their apartment like his did.)

That said, if you do get your teeth whitened, it's definitely worth consulting with a professional, so there's less risk of ending up with a smile that glows in the dark. That's why we spoke to the New York-based Dr. Sonia Kohli, DDS, about what you need to know before whitening your teeth.

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Kohli says if your teeth are stained and not as bright as they should be — and if you often drink things that could change the color of your teeth like red wine and coffee — then it might be a good time to consider getting those teeth to shine bright like a diamond.

Your dentist will do a full evaluation with you to check out the health of your mouth and any other teeth issues, as well as talking about your lifestyle to see if teeth whitening is for you.

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Kohli recommends looking into what concentration of carbamide peroxide is being used for the specific treatment you would like to do. There are various strengths on the market, so consult with your dentist about which one is best for you. They should know about problems that could arise due to sensitivity, etc. You can read more about the kinds of teeth whitener out there here.

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"The one I like most is called Zoom," says Kohli. "It's an in-house treatment and only takes an hour of chair time as it's four treatments back to back for 15 minutes each."

The only drawback? Well, it'll cost a pretty penny: The average cost of this treatment is about $500 (which includes the take-home pack for aftercare). And since it's a cosmetic procedure, your health insurance probably won't cover it.

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About six months, according to Kohli. Depending on what you consume, that is: If you love red wine, cola, anything with artificial colorants that can stain your teeth, then you might need touch ups sooner, she explains.

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