월스트리트저널화요일, 10. 9월 2013, 08:26:00 KST

Timing Your Teeth Brushing

When It May Be Better to Rinse and Wait

Cavity Culprits

Sugary foods, particularly those that are sticky or liquid, are bad for your teeth because the bacteria or plaque on the enamel metabolizes sugars, producing acids that can lead to gum disease, inflammation and cavities. Conventional wisdom held that if you remove the food particles quickly after they were introduced into the mouth, you would reduce the instance of cavities. "What we found is that much of the cariogenic substances, those things that cause cavities, are not only sugar-containing, but they are very acidic themselves," says Dr. Cole.

Too Much Acid

"When you eat or drink something acidic, the pH in your mouth goes down and can take some time to go back to normal." The ideal pH of a mouth is about 7, while a soda—even a diet one—can be as low as 2.5 or "about the same as household vinegar," says Dr. Cole. Acid demineralizes and weakens the tooth surface, making it more prone to decay.

Scrubbing with a toothbrush can actually encourage the process, according to a study published in the journal General Dentistry in 2004. "When you want to make etched glass, you apply an acid or an abrasive and scratch it—that is what happens if you drink a sports drink or a soda, or even wine, and brush right after," says Dr. Cole. If you wait 30 minutes, however, "the saliva in your mouth will naturally bring the acid down to a more neutral pH and not rub acidic substances in."

Rinse, Repeat

Rinsing with water has actually been shown to balance the mouth's pH after ingesting acidic food and beverages. "We tell patients that, once you're done drinking, the best thing to do is to just rinse your mouth out with water," says Dr. Cole. "It's better than brushing within that first 30 minutes." An antibacterial mouthwash can help prevent the plaque from producing more acids, so keeping a little bottle in your office drawer isn't a bad idea, either.

Cheese Whiz

Studies show two things people can chew to help ward off tooth decay. One, Dr. Cole says, is chewy cheese: String cheese will reduce the pH of bacterial plaque. One reason, says Dr. Cole, is that chewy things make you salivate, and proteins in your saliva will buffer acids. Also, naturally occurring chemicals in cheese "encourage the tooth to remineralize." Dr. Cole suggests: "The pairing of wine with cheese is actually a good thing, because the cheese can counterbalance the acidity of the wine."

Chewing sugarless gum is also a good option if you can't get to your toothbrush. "Some studies have suggested that xylitol, which is the sweetening agent in gum, actually has anticariogenic characteristics."

Bedtime

Dentists like Dr. Cole suggest brushing twice a day, for two minutes each time. If you can only do it once, bedtime is best, since that is when your mouth salivates less, allowing cavity-causing substances to take hold. Rinsing after sipping sugary drinks is always a good idea. "I'm guilty of craving a Coke now and then just like anyone else," says Dr. Cole. "But after I will go and rinse that acid and sugar out with some plain water."

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