13 Things Dentists Never Put in Their Mouth

Updated: Jun. 22, 2022

Dentists see countless patients each year who break teeth because they chomp on the wrong thing—food or otherwise. Here are the things the pros beg you to keep out of your mouth.

Dentist tips

Dentists know all about good oral hygiene, but taking care of your teeth is more than just brushing and flossing twice a day. In fact, there are some things that dentists never put in their mouths—so neither should you. From ice to lemons, here are the things to avoid to maintain a healthy smile.

lemon slices


They’re a fruit after all—so how much harm could they cause? As it turns out, a whole lot. People have a habit of sucking on lemons and keeping them in their mouth for longer than they would other food, explains Victoria Veytsman, MD, a New York City dentist. Because lemons are so acidic, she warns this can lead to enamel erosion and also throws off the mouth’s ideal balance of acids and bases, known as pH balance.

ice cubes
Pan Stock/Shutterstock


For whatever reason, many people love to chew on ice or ice chips. But doing so sets up a battle between your teeth and the ice. In fact, dentist Peter Vanstrom, DDS, has seen many cases each year where the ice cube has won and a tooth or several teeth are fractured. “These fractured teeth may require crowns to restore proper function and stability,” he says. Instead of munching on ice, he recommends sipping chilled beverages or using a straw so you’re not tempted to crunch.

pile of green beer caps

Metal bottle caps

When you don’t have a bottle opener, it can be tempting to use your teeth, but this is a major no-no according to dentists. “If you break a tooth down the middle, you may lose the tooth entirely and need an implant and implant crown,” says Bill Dorfman, DDS, Beverly Hills-based cosmetic dentist. “It’s just not worth it.” Instead, wait until you have a bottle opener or at least another instrument besides your teeth to crank it open. (Here are 11 things your dentist wants you to start doing differently.)

plastic bottle caps
Jiri Vaclavek/Shutterstock

Plastic bottle tops

Just like bottle caps, plastic bottle tops can be a pain to open. But resist the temptation to put the plastic top in your mouth, bite down and then twist to loosen the cap. “This can not only cause teeth fractures but muscle and temporomandibular joint [TMJ] pain and problems,” warns Dr. Vanstrom. “That twist of your head and jaw put a quite a bit of strain on your chewing muscles and joints.” Instead, avoid teeth fractures, muscle pain, and TMJ problems by using your hands.

toothbrush bristles

Other people’s toothbrushes

Whether it’s your significant other’s or your best friend’s, resist the temptation to borrow a toothbrusheven if it’s just for one night. “Not only are they full of bacteria, but the biggest risk is that, if the person is sick or about to get sick, you will too,” warns Dr. Dorfman. “There are also studies that suggest that the bacteria that cause tooth decay can be spread through sharing toothbrushes.”

extreme closeup of a male finger detail
Aaron Amat/Shutterstock

Your nails

When it comes to harmful nervous habits, biting your nails might not be the worst. But Lana Rozenberg, DDS, a New York City-based dentist, warns that the habit can flatten the edges of your front teeth. “Over time, your teeth can wear faster and nail-biting can create cracks on the enamel of your teeth until they become hypersensitive,” she says. “The biting action also puts your jaw in an unnatural position that can stress your joints, can cause grinding and clenching—and this prolonged pressure and friction can cause pain in your teeth, ears, and jaw.”

colorful hard candy
Ruth Black/Shutterstock

Hard candies

“Hard candy lingers in the mouth for a long time as you wait for it to dissolve and deliver sugary goodness,” says Dr. Rozenberg. “It could take up to 10 minutes for some hard candies to dissolve and there are no health benefits associated with hard candy.” If you’re not patient enough to wait until the candy is dissolved, chewing on it can lead to cracked teeth and cuts on the inside of the mouth. (Read up on secrets your dentist won’t even tell you.)

A Pile of old Keys different shapes, sizes and colors
Nataliia Zhekova/Shutterstock


When you’re walking to or from your car and are carrying more items than you have hands for, it can be tempting to slide your keys in your mouth and bite down to hold them, but this can cost you that perfect smile. “Keys are a culprit for chipped or cracked teeth,” warns Dr. Vanstrom. “Keys are also filled with bacteria that can make you sick, so when in doubt, put the bags down and open the car or door.”

colorful paper clips

Pens, paper clips, and erasers

“People have chewed on pencils, pens, the metal support of erasers, and paper clips for generations—and, for generations, people have been breaking teeth,” says Dr. Vanstrom. While it’s tempting to chew on your pen or eraser when you’re bored, he recommends instead opting for sugar-free gum. This way, you’re not putting a bacteria-riddled item in your mouth and you’re preserving your smile.

jewelry hanging with clothespins
Courtesy A Pair & A Spare


Facial piercings might be trendy, but studs and rings create breeding grounds for infection, not to mention cause bleeding and swelling of the tongue or nearby tissue. Additionally, Dr. Rozenberg points out that tongue, cheek, or lip jewelry can cause chronic injury to adjacent teeth and mucosa (the cheeks, lips, taste buds), including tooth fractures and gum recession, which can lead to tooth loss.

potato chips

Potato chips

They may be undeniably tasty and satisfying (at least while they’re still in our mouth), but potato chips are no good for your chompers. “They’re loaded with starch, which becomes sugar that can get trapped in and between the teeth and feed the bacteria in the plaque,” says Dr. Rozenberg. “Since we rarely have just one, the acid production from the chips lingers and lasts a while.”

a lot of burnt cigarette butts with some ash
Dario Lo Presti/Shutterstock


You’re probably well aware of the fact that cigarettes are terrible for your health and the cause of cancer and a myriad of other diseases. Not only are they very bad for your overall health, but they’re really hard on your mouth. “In addition to being one of the major causes of oral cancer, cigarettes stain teeth and cause halitosis (bad breath),” says Dr. Veytsman. (Need help? Here are 22 great way to kick the habit.)

parking garage exit gate
xiao yu/Shutterstock

Parking vouchers

It might sound strange, but Dr. Dorfman constantly sees people pull these from the machine in a garage and put them in their mouths while they park. Not only are parking vouchers, or anything you receive from a public space like a parking garage, not sterile, but they do nothing for your teeth. Often printed on thermal paper, they’re loaded with chemicals that are bad for your mouth and your body.

Next, find out the foods dentists never eat, so you should avoid them too.

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