Toothpaste marketers have long pitched enamel-strengthening toothpastes they claim harden the tooth’s protective layer, thereby making it more resistant to attacks from acids found in food and beverages like soda, orange juice and even pickles. Scientists are in agreement these toothpastes do make enamel more acid-resistant—but not nearly enough to protect you if you chug soda all day.

Enamel is a thin covering over teeth made from an organic matrix and minerals, largely crystals of calcium phosphate, says Therametric Technologies Inc., a Noblesville firm that sells and tests dental products. Enamel is vulnerable both to decay, caused by acids in bacteria, and to erosion, defined as direct assault from acids from food and drink. The biggest offenders include diet and regular sodas, citrus beverages, red wine and some sports drinks.

While everyone is vulnerable to acid erosion, the problem worsens as we age due to a decrease in production of saliva—which both washes away acids and neutralizes them. Certain medications also decrease saliva production.

What’s an Acid Fighter?

A number of toothpastes that claim to combat acid erosion and strengthen enamel are now on the market. Crest Pro-Health Enamel Shield’s label says it “protects against acid attack.” Sensodyne ProNamel says it “protects against the effects of acid erosion.” Colgate Total’s line includes an “Enamel Strength” version. A CVS store brand promises it “helps harden tooth enamel with acid protection formula.”

The claims are often based on the presence of fluoride, which scientists say combines with minerals in your mouth to create a crystal called fluorapatite on the surface of your teeth. Some of the toothpastes, including Crest’s Enamel Shield, Sensodyne ProNamel and Squigle Inc.’s Enamel Saver, are also formulated to be less abrasive to protect your enamel from rubbing off when brushing. (Squigle is a manufacturer of a small brand of toothpastes it says are non-irritating to the mouth.)

Scientists give mixed reviews to the claims. They say it is incorrect to say a toothpaste can strengthen enamel as it doesn’t make teeth physically stronger against shearing forces—such as biting into a piece of popcorn. The products do make the tooth surface more resistant to acids in the diet, says John Featherstone, dean of the University of California School of Dentistry in San Francisco.

While dentists agree toothpastes can help protect enamel, you should still drink acidic beverages in moderation. “You can’t drink erosive foods and drinks in high frequency and expect a toothpaste to protect you,” says Mark S. Wolff, a professor and chairman of the department of cariology and comprehensive care at New York University College of Dentistry. (Cariology is the study of tooth decay.)

Regardless of the toothpaste you use, it is important not to brush your teeth immediately after drinking acids as that is when enamel is most vulnerable to wear from brushing, adds Teresa Marshall, an associate professor at the University of Iowa College of Dentistry in Iowa City. It’s a good idea to take a few sips of water after drinking or eating acids, scientists add, and sugar-free gum can help by stimulating saliva production.

Label Study

As for toothpastes touting enamel strengthening, an informal inspection of labels in pharmacy aisles found the toothpastes often had nearly identical ingredients to other products by the same manufacturers that don’t make enamel claims. Some of the distinction, companies say, involves proprietary differences in proportions of ingredients.

Scientists say any well-designed fluoride toothpaste will make enamel more acid resistant. The enamel-strengthening claims on the label are “a marketing gimmick,” says Dr. Featherstone, who has done paid consulting for a number of toothpaste makers. Consumers should choose a toothpaste with a taste they like, as they’ll use it more, he says. He recommends major brands because a lot of research goes into proper formulation.

Procter & Gamble says its Crest Pro-Health Enamel Shield is the result of more than a decade of research and seven separate inventions. The company says the term “strengthens enamel” on the label refers to making teeth more chemically resistant to acid. GlaxoSmithKline, maker of Sensodyne ProNamel, says that, while fluoride doesn’t significantly harden normal tooth enamel it does have a hardening effect on enamel which has been softened by acid erosion. Colgate-Palmolive declined to be interviewed.

At least two companies—P&G and GlaxoSmithKline—have published studies showing their toothpastes help protect enamel in test subjects wearing either crowns or appliances with test teeth in them. (This type of research allows scientists to perform controlled tests, such as deliberately creating acid erosion on the test teeth.) However, there aren’t enough well-designed studies directly comparing one toothpaste with another to determine if one toothpaste is really better than another, scientists say.

Can “Extra Fluoride” Help?

Based on ingredients, there are some differentiation points. Colgate’s new ProClinical Daily Renewal for Enamel, has 1,500 parts per million of fluoride—more than most toothpastes, according to the company’s website. Sensodyne ProNamel is specially formulated so that more fluoride is available, enhancing the process of remineralizing enamel, GlaxoSmithKline says. Scientists say extra fluoride is likely to have at least a small additional effect on enamel—but more research is needed.

P&G’s Crest Pro-Health Enamel Shield, which came out last year, is made with a particular type of fluoride called stannous fluoride. In addition to forming fluorapatite crystals like other fluorides, stannous fluoride also has a toxic effect on acid-producing mouth bacteria, says biochemist Matthew J. Doyle, director of global research and development for P&G’s oral-care division. Stannous fluoride also protects against tooth sensitivity by blocking small tunnels in the teeth, he adds.

Crest’s Pro-Health Enamel Shield also has sodium hexametaphosphate, an ingredient that forms a protective film over the teeth that lasts six or seven hours. “It’s a sacrificial layer that protects the surface of the tooth,” Dr. Doyle says.