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A final filter can “remineralize” the water, usually adding back calcium, magnesium and adjusting the acidity.

The soil in his area is particularly depleted of calcium, so he imports limestone to remineralize the soil.

If they demineralize at a quicker rate than they remineralize, you get a cavity, said Dr. Burton Edelstein, a professor of dentistry and health policy at Columbia University.

Conversely, it is possible to remineralize a decaying tooth by arresting the disease process, he said.

“You need to give your teeth time to remineralize after being bathed in an acidic beverage,” says Maureen McAndrew, clinical professor at the New York University School of Dentistry.