It's a sad fact of life: Soft drinks and fruit juice aren't very good for you, and they can be particularly hard on your teeth. German researchers have found out exactly why that is, based on an analysis so simple it might not qualify for the high school science fair: seeing how much tooth is left after it's left to soak in some tasty beverage for a while.
As demand for soda and juice increase worldwide, there's been concern about the impact that these liquids have on our teeth. Acids in those beverages—phosphoric, carbonic, citric, and so on—may well be behind the increasing rates of tooth decay worldwide, but the exact effect of a given drink on our teeth is hard to measure efficiently. Some measurement techniques only capture erosion at the surface, or enamel, of the tooth, and it's often difficult to determine how much tooth erosion a particular drink causes.
What to do? "A possible simple and meaningful method may be gravimetric analysis," writes a team led by Stefan Zimmer, a professor of dentistry at Witten/Herdecke University in Witten, Germany, in the journal PLoS One.
Zimmer and him team got a bunch of teeth, weighed them, soaked them in everything from swimming pool water to Red Bull, then weighed them again.
"Gravimetric analysis," in case you're wondering, isn't a groundbreaking new technique; it's just weighing stuff on a scale. Rather than apply sophisticated techniques including, in the extreme case, atomic absorption spectroscopy, Zimmer and him team got a bunch of teeth, weighed them, soaked them in everything from swimming pool water to Red Bull, then weighed them again.
The researchers first collected 200 one-millimeter thick samples of enamel and dentin, the middle tooth layer, from cow incisors. After weighing those samples, they placed the samples in cups containing one of 10 fluids: tap water, chlorinated swimming pool water, apple juice, orange juice, lemon juice, Coke, Diet Coke, Sprite, Red Bull, and something called BonAqua Fruits. After seven days submerged in each liquid, the researchers removed the enamel and dentin samples, washed them in salt water, and re-weighed.
Lemon juice was the worst for your teeth—not surprising, given its high acidity. Sprite and apple juice ranked high as well. Initially, the tooth samples weighed about 36 milligrams on average. After a week, lemon juice ate most of that up, consuming about 32 milligrams of enamel or dentin per sample on average. Sprite and apple juice scarfed down slightly less tooth matter on average—26 and 27 milligrams, respectively. Water, whether from the tap or the pool, had no effect on teeth.
Interestingly, acidity alone doesn't drive the results. Coke, for instance, has nearly the same acidity as Sprite, but it consumed only five milligrams of tooth on average over the week.
Likewise, acidity alone shouldn't drive dentists' recommendations. "Despite its high erosivity, orange juice may be a valuable contribution to a healthy nutrition whereas other non alcoholic drinks with low erosivity are not," Zimmer and his team write.
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