After a teeth-whitening treatment, you’ll probably grin into any reflective surface available—mirrors, windows, other people’s sunglasses—to lovingly admire your white teeth. But at some point, perhaps as you snap your bedtime selfie, you might be struck with a sense of dread: how am I going to keep this up?

Never fear. We talked to Kimberley Watry, co-owner of Chicago’s Smiling Bright teeth-whitening clinic, to find out how to keep those bright white results from yellowing.

What results should you expect?

It depends on the current state of your teeth. If they’re yellowish, factors like coffee, wine, and smoking are probably to blame, and the stains should come off easily. Watry said whitening can turn yellow teeth back to the color they were when they grew in.

If you’re an older person with grayish teeth, that’s probably due to the antibiotic tetracycline, which is less widely used today. That gray tone is hard to remove, but it can be done. The only type of stain that doesn’t budge? Faint bloodstains due to long-ago fisticuffs. Watry said you’ll probably have to live with those.

Last but not least, if you’re intending on getting dental work like veneers or crowns, make sure to have your teeth whitened before the procedure. That way, your dentist can match the work to your brightest teeth. (Clients who already have veneers or crowns can expect stain removal that returns them to the original, manufacturer-issued shade.)

What does proper teeth-whitening aftercare look like?

Brushing your teeth twice a day and flossing daily. Many clients ask Watry for recommendations about whitening toothpaste, but she advises them to go for a more bare-bones approach.

“I always say just to buy what’s on sale. It’s a marketing ploy. Hydrogen peroxide is [often] what is the active ingredient.” It might be better, she said, to go straight to the source: “Buy that brown bottle of hydrogen peroxide that you can get at the grocery store or drugstore—it’s 3% hydrogen peroxide—and gargle with that right after you brush your teeth, morning and night. It really does help maintain it. And it’s affordable!”

Also, try to brush immediately after meals to avoid stains. Stow a portable toothbrush and tube of toothpaste in your bag, or opt for a disposable, two-in-one version, like Colgate’s Wisp.

Can you eat and drink whatever you want?

It depends on the kind of lifestyle you want. But according to Watry, you should first strive to enjoy your life, then to whiten your teeth.

“If you think it’s going to stain your T-shirt, it’s going to stain your teeth. It’s salsa, it’s ketchup, it’s mustard, it’s soy sauce, it’s marinara sauce, it’s anything that tastes good. Coffee, tea, chocolate, you know what I mean?” she said. “So you’d be down to crackers and melons and cereal and turkey.”

Stains may be mitigated by sipping through a straw or rinsing with water, but Watry advocates just brushing your teeth afterward.

When should you go back for more?

Generally, if you practice good dental hygiene, you can expect to need a touchup around the 12-month mark. Heavier smokers, though, may need a whitening touchup after six months. There’s no set timetable, though.

“I always compare it to this,” Watry said. “No one can tell you how often you need your hair cut, because you just wake up one morning and you’re like, ‘Uergh, I need my hair cut.’ Same with your teeth. You’re going to wake up one morning and you’ll be like, ‘Ooph, it’s time for a touchup!’’

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