By Karen Hopkin
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Fluoride helps fight cavities. That's why it's in our drinking water and toothpaste. But how this mineral works its dental magic is still somewhat mysterious. Now, researchers offer an incisive solution. They find that fluoride treatment can loosen bacteria's grip on tooth enamel. The study is in the journal Langmuir. [Peter Loskill et al., Reduced Adhesion of Oral Bacteria on Hydroxyapatite by Fluoride Treatment]
Scientists used to think that fluoride could harden tooth enamel, helping it retain the minerals that protect teeth from the acid produced by our oral flora. But recent work has shown that fluoride doesn't really penetrate past the tooth's thinnest outer layer, suggesting that something other than hardening is going on.
To drill deeper into this toothsome mystery, researchers whipped up a set of artificial choppers, made of the same stuff as teeth. And they used atomic force microscopy to take a closer look at how bacteria interact with this dental material. They found that three different strains of cavity-causing bugs cling less tightly to enamel that's been rinsed with fluoride.
The bacteria carry a net negative charge on their surfaces. So the negatively charged fluoride ions in the treated enamel may be literally repulsive to the bacteria. Which causes them to bite the dust.
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While dried fruits may be a definite <a href="http://www.huffingtonpost.com/2012/02/28/fruit-chew-snacks-ingredients_n_1304369.html">step up from processed fruit snacks</a>, they are still sticky and high in sugar. That means they not only adhere to teeth easily, but the sugar feeds the bacteria in the mouth, which can promote dental erosion, notes Joy Dubost, Ph.D., R.D., a spokesperson for the American Academy of Nutrition and Dietetics. "I'm not saying don't eat them, but just brush your teeth afterward," Dubost says. Messina adds that regular fresh fruits don't typically have this problem because -- even though they still have sugar -- chewing them up promotes saliva and they don't stick to the teeth. "Fruits are generally pretty safe because they're good for overall health <em>and</em> they're chewy, so your average fruit has some substance to it and we chew through it, causing us to salivate more," Messina says. "Saliva is a good thing because it has washing action and it's a nautral buffer [to] acid."
Sugary drinks, such as sodas and sports drinks, are especially bad for teeth when sipping for long periods of time. "If I have a soft drink or sports drink and I'm sipping it every 20 minutes, my teeth are getting bathed with a constant layer of acid," Messina says. "So sitting down and drinking it all at once, or with a meal, is better than snacking or sipping throughout a meal." For this reason, Dubost recommends that parents don't fill their kids' sippy cups with sugary drinks, since kids, whose teeth are still developing, tend to sip at those drinks over long periods of time.
For the same reason sipping on sodas all day is bad for teeth, hard candies aren't ideal for oral health, Dubost notes. These sweets pack a double whammy in that they not only stick to the teeth, but they also linger in the mouth for a long time as you wait for them to dissolve.
You may not realize it, but alcohol can be bad for the teeth, as it causes <a href="http://www.yalemedicalgroup.org/stw/Page.asp?PageID=STW001565">natural saliva production</a> to decrease, according to the Yale Medical Group. And again, saliva helps to wash away food particles and provides a buffer against acid. People who are alcoholics may <a href="http://www.thefix.com/content/sober-teeth?page=all">experience dental and gum disease</a> since "alcohol irritates all the soft tissue in the mouth and it decreases the amount of natural saliva," Dr. Parimal Nagjee, a dentist in Beverly Hills, <a href="http://www.thefix.com/content/sober-teeth?page=all">told The Fix</a>. "In terms of the tissue, the skin of the mouth is very delicate and the alcohol is corrosive to the gums, cheeks and skin. It can affect the way the tissue cells divide, which is why people who drink heavily have a greater chance of getting mouth or throat cancer.”
Foods high in acid, such as citrus or tomatoes, can promote tooth decay, especially when eaten alone, Dubost notes. But these foods are fine to eat so long as you flush your mouth with water after consuming them in order to buffer the acid. Citrus not only has acid, but also sugar -- and people who have a habit of sucking on lemons or limes are actually harmfully bathing their teeth in acid, Messina says. "If you look in their mouths, their teeth have a shiny, glossy surface -- that's from constant bathing with the acids," he says. "They will have almost a peculiar look in that you'll see it on the front surfaces of their teeth, but not the back sides of the lower front teeth because those are under the tongue -- and the tongue protects the surface of teeth."
Starchy foods, such as potato chips and white bread, easily get trapped in teeth, which can then <a href="http://www.yalemedicalgroup.org/stw/Page.asp?PageID=STW001565">feed the bacteria</a> that make up plaque, according to the Yale Medical Group.
Not only do drinks like coffee and tea stain the teeth, they also make the teeth stickier -- meaning more food particles can latch on, Messina says.
Worst Foods For Your Teeth
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