The potential key to upgrading toothpaste? Sheep’s wool and human hair.

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The next major innovation in dental care just might be a new ingredient added to our toothpaste and mouthwash from an unlikely source: sheep’s wool or human hair.

Both contain the fibrous protein keratin, which can repair damaged tooth enamel, according to an international study led by researchers at King’s College London.

The scientists found that keratin can stop the early stages of tooth decay, a problem that afflicts about 90 percent of American adults aged 20 to 64 years, according to the National Institute of Dental and Craniofacial Research, part of the National Institutes of Health.

Reporting this week in the journal Advanced Healthcare Materials, the researchers said that when keratin mixes with the minerals found in saliva, such as calcium and phosphate, it forms a coating that mimics the structure of natural enamel and is comparable in strength.

Tooth enamel, the protective outer layer shielding teeth, is the hardest substance in the human body, but it can be worn away by acidic foods and beverages, acid reflux, dry mouth, poor brushing and flossing, and the nighttime grinding that can occur when we sleep.

While other parts of the human body have the capacity to regenerate – fingernails, skin, bone, blood vessels and the liver – enamel cannot.

“Unfortunately, once you lose the enamel it doesn’t come back. It’s gone forever,” said Sherif Elsharkawy, senior author of the new paper and a senior clinical lecturer in prosthodontics at King’s College London. Prosthodontics is the branch of dentistry dealing with the design, manufacture and fitting of artificial replacements for teeth and other parts of the mouth.

A 2014 paper suggested that hair keratin is important to tooth enamel. Researchers who worked on the study found that people with mutations in the keratin were at increased risk of dental decay.

Keratin is already found in shampoos, conditioners, skin moisturizers and lotions, and food like eggs and salmon promote keratin production.

“It’s extremely safe,” Elsharkawy said.

While keratin has yet to be added to any commercially available toothpaste or mouthwash, that might be only two or three years away, according to Elsharkawy. He also envisions a gel that dentists could use when treating patients with damaged enamel.

Martinna Bertolini, an assistant professor of periodontics and preventive dentistry at the University of Pittsburgh School of Dental Medicine who was not involved in the study, said, “Overall, I think it’s promising as a future formulation, though this paper didn’t test a real product, so formulation, safety, taste, dosing and clinical trials still lie ahead.”

Elsharkawy’s team, which included scientists from the University of Toronto, the Chalmers University of Technology in Gothenburg, Sweden, and the University of Trento in Italy, tested the keratin using an artificial saliva that has a similar concentrations of elements to our own. They applied the mix to human teeth with lab-created decay and found the treatment filled in the gaps in the enamel and outperformed a plastic resin currently used to treat early decay lesions.

Elsharkawy said the keratin treatment formed a shield that was five to six times harder than the one created by the plastic resin.

Bertolini said it would not be difficult to adjust the chemical components that the researchers used, which should make it simpler to translate their lab results into a product that will work in a dentist’s office.

Sami Dogan, a professor of restorative dentistry at the University of Washington who was not involved in the study, called keratin “a very promising technology,” for enamel repair, but one that is in the very early stages of development and may still be a decade or more from reaching the market.

One clear advantage it would have, he said, is that “keratin from the get-go is very cheap and it’s also abundant.”

Dogan has been working with other researchers on a peptide, a short chain of amino acids, designed to rebuild worn tooth enamel and cover sensitive tissue with “mineral microlayers.” The technique would closely resemble the way the body develops teeth.

Dogan said he could foresee using both methods – the keratin scaffold and the peptide – to treat deep cavities.

Tim Wright, editor in chief of the Journal of the American Dental Association, and a professor at the Adams School of Dentistry at the University of North Carolina, said that there are existing methods of creating dental scaffolding that “are modestly successful.”

While he said there is still a need to develop more effective and cheaper alternatives, he is far from sold on the keratin results in the new paper.

“It’s got promise, but I would want to see it in an actual clinical trial,” he said.

Elsharkawy remains confident. He said researchers intend to conduct a clinical study to learn more about the mechanism and get a better understanding of the most effective dose.

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