Four out of five people think that sugar causes cavities, but that’s not true. The real culprits are bacteria in the mouth that feed on sugar and other carbs, then release acids that dissolve tooth enamel, weakening and eroding it to the point where cavities can form.

Certain behaviors—including some that are sure to surprise you, such as kissing!—increase your risk for dental decay. Matthew J. Messina, DDS, a national spokesperson for the American Dental Association and a dentist in private practice in Fairview Park, Ohio, explained how to guard against startling causes of cavities, including…

French kissing. Smooching can transfer bacteria such as Streptococcus mutans from your sweetheart’s mouth to yours—and vice versa. When those bacteria produce acids, cavity risk increases.

Prevention: You and your partner must practice good oral hygiene to protect each other. This means brushing twice each day with a tooth-strengthening fluoride toothpaste and flossing daily. It’s also smart to brush the surface of your tongue once a day. “You can use a toothbrush. Just stick out your tongue and hold the tip with your nonbrushing hand, then scrape the tongue’s surface lightly,” Dr. Messina said. Also ask your dentist whether an antibacterial mouthwash would be beneficial for you. If you and your partner follow these steps, the bacteria levels in your mouths should be low enough that tongue-touching kisses won’t increase your cavity risk.

What if your honey does not practice good oral hygiene? Give your partner a new toothbrush and fluoride toothpaste. Lovingly suggest that a trip to the dentist and improved oral hygiene could help banish bad breath and other turnoffs, making make him or her more kissable. Dr. Messina did not recommend scare tactics, such as showing your partner a disgusting close-up image of bacteria eating away at dirty teeth—but you can explain that poor oral health may be linked to heart disease and other health problems.

Sipping sweet drinks. The sugar in soda, energy drinks and sports drinks is bad enough because it feeds those acid-producing bacteria. This problem is compounded, however, because these beverages also contain acids (such as citric, carbonic, malic and/or phosphoric acid) that skew the acid/alkaline balance inside the mouth.

Normally the mouth has a neutral pH of 7.0. Tooth dentin (the root and inside part of the tooth) starts to dissolve at a pH of 6.5, while enamel starts to dissolve at a pH of 5.5. Regular and diet soft drinks, energy drinks, sports drinks and citrus juices have a pH of 2.3 to 4.0—levels that can dissolve rust, Dr. Messina said. Sipping such beverages is especially damaging because it prolongs the “acid bath” that your teeth must soak in.

Prevention: Drink water instead. Or if you can’t resist the allure of a sweet beverage, drink it more quickly rather than sipping…or at least use a straw to help keep the fluid away from your teeth. When you’re done with your drink, immediately rinse your mouth with water. Don’t brush right away, though—the acid leaves enamel soft and vulnerable. Wait 30 minutes for the enamel to harden up before you brush, Dr. Messina advised. (Watch this video, and you’ll never have a sweet drink again.)

Too-vigorous tooth-brushing. Forceful brushing causes gums to recede, exposing part of the roots of the teeth. The roots are covered with cementum, which is softer than enamel and thus more vulnerable to decay (not to mention more sensitive to pain). Older adults are particularly prone to cavities at the gum line.

Prevention: Use a soft toothbrush to gently clean all the surfaces of the teeth. At the gum line especially, think of using those bristles to massage, not to scrub, Dr. Messina suggested. Many people brush improperly, so watch this video to learn the right way to brush, especially in hard-to-reach spots.

Using mouth-drying drugs. Saliva is a natural buffer against cavities because it helps neutralize acids and washes food particles away from teeth. More than 400 prescription and over-the-counter medications can reduce saliva production, leaving you with a dry, cavity-prone mouth. These include certain drugs that treat depression, high blood pressure, diarrhea and urinary incontinence, as well chemotherapy drugs, antihistamines and decongestants.

Prevention: Chew sugarless gum sweetened with xylitol to stimulate saliva flow, and drink plenty of water to keep your mouth hydrated. Don’t smoke! Along with all its other catastrophic health effects, smoking dries out your mouth. Also, tell your dentist about all prescription and over-the-counter medications and supplements you take and whether you experience dry mouth. Together, your dentist and doctor may be able to find alternative treatments that do not have this side effect.

Ignoring old fillings. Dental fillings can weaken, loosen or crack over time, creating tiny crevices in which acid-producing bacteria can build up. Yet it is difficult for the average person to tell whether there is a problem with an old filling that is starting to fail, Dr. Messina said.

Prevention: Have your teeth professionally examined at least twice a year—so worn-out fillings can be replaced before bacteria have a chance to make your old cavities even worse.