Teeth are essential for helping people break down the food they eat, and are protected by enamel, which helps them withstand the large amount of stress they experience as people chew away. Unlike other materials in the body, enamel has no way to repair damage, which means that as we age, it risks becoming weaker with time.

Researchers are interested in understanding how enamel changes with age so that they can start to develop methods that can keep teeth happier and healthier for longer.

A research team at the 天美影视传媒 and the Pacific Northwest National Laboratory examined the atomic composition of enamel samples from two human teeth 鈥� one from a 22-year-old and one from a 56-year-old. The sample from the older person contained higher levels of the ion fluoride, which is often found in drinking water and toothpaste, where it鈥檚 added as a way to help protect enamel (though its addition to drinking water has recently been a ).

The team Dec. 19 in Communications Materials. While this is a proof-of-concept study, these results have implications for how fluoride is taken up and integrated into enamel as people age, the researchers said.

“We know that teeth get more brittle as people age, especially near the very outer surface, which is where cracks start,” said lead author , UW doctoral student in materials science and engineering and a doctoral intern at PNNL. “There are a number of factors behind this 鈥� one of which is the composition of the mineral content. We’re interested in understanding exactly how the mineral content is changing. And if you want to see that, you have to look at the scale of atoms.”

Enamel is composed mostly of minerals that are arranged in repetitive structures that are ten thousand times smaller than the width of a human hair.

“In the past, everything that we’ve done in my lab is on a much larger scale 鈥� maybe a tenth the size of a human hair,” said co-senior author , UW professor of materials science and engineering. “On that scale, it’s impossible to see the distribution of the relative mineral and organic portions of the enamel crystalline structure.”

To examine the atomic composition of these structures, Grimm worked with , a materials scientist at PNNL, to use a technique called “atom probe tomography,” which allows researchers to get a 3D map of each atom in space in a sample.

The team made three samples from each of the two teeth in the study and then compared differences in element composition in three different areas of the tiny, repetitive structures: the core of a structure, a “shell” coating the core, and the space between the shells.

In the samples from the older tooth, fluoride levels were higher across most of the regions. But they were especially high in the shell regions.

“We are getting exposed to fluoride through our toothpaste and drinking water and no one has been able to track that in an actual tooth at this scale. Is that fluoride actually being incorporated over time? Now we’re starting to be able to paint that picture,” said co-author , a postdoctoral researcher in both the oral health sciences and the materials science and engineering departments at the UW. “Of course, the ideal sample would be a tooth from someone who had documented every time they drank fluoridated versus non-fluoridated water, as well as how much acidic food and drink they consumed, but that’s not really feasible. So this is a starting point.”

The key to this research, the team said, is the interdisciplinary nature of the work.

“I am a metallurgist by training and didn’t start to study biomaterials until 2015 when I met Dwayne. We started to talk about the potential synergy between our areas of expertise 鈥� how we can look at these small scales to start to understand how biomaterials behave,” Devaraj said. “And then in 2019 Jack joined the group as a doctoral student and helped us look at this problem in depth. Interdisciplinary science can facilitate innovation, and hopefully we’ll continue to address really interesting questions surrounding what happens to teeth as we age.”

One thing the researchers are interested in studying is how protein composition of enamel changes over time.

“We set out trying to identify the distribution of the organic content in enamel, and whether the tiny amount of protein present in enamel actually goes away as we age. But when we looked at these results, one of the things that was most obvious was actually this distribution of fluoride around the crystalline structure,” Arola said. “I don’t think we have a public service announcement yet about how aging affects teeth in general. The jury is still out on that. The message from dentistry is pretty strong: You should try to utilize fluoride or fluoridated products to be able to fight the potential for tooth decay.”

, a postdoctoral researcher at PNNL, is also a co-author on this paper.聽This research was funded by the National Institutes of Health, Colgate-Palmolive Company and a distinguished graduate research program between PNNL and UW.

For more information, contact Grimm at jckgrmm@uw.edu, Arola at darola@uw.edu and Renteria at crentb@uw.edu. For questions specifically for Arun Devaraj please contact Karyn Hede at karyn.hede@pnnl.gov.

Current advice from the tells you that if your gums bleed, make sure you are brushing and flossing twice a day because it could be a sign of gingivitis, an early stage of periodontal disease. And that might be true. So if you are concerned, see your dentist. However, a new 天美影视传媒 study suggests you should also check your intake of vitamin C.

鈥淲hen you see your gums bleed, the first thing you should think about is not, I should brush more. You should try to figure out why your gums are bleeding. And vitamin C deficiency is one possible reason,鈥� said the study鈥檚 lead author , a practicing dentist and professor of oral health sciences in the UW School of Dentistry.

Hujoel鈥檚 study, , analyzed published studies of 15 clinical trials in six countries, involving 1,140 predominantly healthy participants, and data from 8,210 U.S. residents surveyed in the Centers for Disease Control and Prevention鈥檚 Health and Nutrition Examination Survey. The results showed that bleeding of the gums on gentle probing, or gingival bleeding tendency, and also bleeding in the eye, or retinal hemorrhaging, were associated with low vitamin C levels in the bloodstream. And, the researchers found that increasing daily intake of vitamin C in those people with low vitamin C plasma levels helped to reverse these bleeding issues.

Of potential relevance, says Hujoel, who is also an adjunct professor of epidemiology in the UW School of Public Health, both a gum bleeding tendency and retinal bleeding could be a sign of general trouble in one鈥檚 microvascular system, of a microvascular bleeding tendency in the brain, heart and kidneys.

The study does not imply that successful reversing of an increased gingival bleeding tendency with vitamin C will prevent strokes or other serious health outcomes, Hujoel stresses. However, the results do suggest that vitamin C recommendations designed primarily to protect against scurvy 鈥� a deadly disease caused by extremely low vitamin C levels 鈥� are too low, and that such a low vitamin C intake can lead to a bleeding tendency, which should not be treated with dental floss.

Consequently, Hujoel does recommend people attempt to keep an eye on their vitamin C intake through incorporation of non-processed foods such as kale, peppers or kiwis into your diet, and if you can鈥檛 find palatable foods rich in vitamin C to consider a supplement of about 100 to 200 milligrams a day.

If someone is on a specialized diet, such as a paleo diet, it鈥檚 important that they take a look at their vitamin C intake, Hujoel said.聽鈥淰itamin C-rich fruits such as kiwis or oranges are rich in sugar and thus typically eliminated from a low-carb diet.”

This avoidance may lead to a vitamin C intake that is too low and is associated with an increased bleeding tendency. People who exclusively eat lean meats and avoid offal, the vitamin-rich organ meats, may be at a particularly high risk for a low vitamin C intake.

The association between gum bleeding and vitamin C levels was recognized more than 30 years ago. In fact, two studies co-authored by former dean of the UW School of Dentistry Paul Robertson (published in and ) identified gum bleeding as a biological marker for vitamin C levels.

However, this connection somehow got lost in dental conversations around bleeding gums.

鈥淭here was a time in the past when gingival bleeding was more generally considered to be a potential marker for a lack of vitamin C. But over time, that鈥檚 been drowned out or marginalized by this overattention to treating the symptom of bleeding with brushing or flossing, rather than treating the cause,鈥� Hujoel said.

Hujoel鈥檚 literature review also determined that 鈥渞etinal hemorrhaging and cerebral strokes are associated with increased gingival bleeding tendency, and that (vitamin C) supplementation reverses the retinal bleeding associated with low (vitamin C) plasma levels.鈥�

So, missing the possible connection between gum bleeding and low levels of vitamin C has the potential to have serious health consequences.

The study authors write: 鈥淎 default prescription of oral hygiene and other periodontal interventions to 鈥榯reat鈥� microvascular pathologies, even if partially effective in reversing gingival bleeding as suggested in this meta-analysis, is risky because it does not address any potential morbidity and mortality associated with the systemic microvascular-related pathologies.鈥�

Co-authors include Tomotaka Kato, Department of Oral Health Sciences, UW School of Dentistry; Isabel Hujoel, Division of Gastroenterology and Hepatology, Mayo Clinic; and Margaux L.A. Hujoel, Department of Biostatistics, Harvard T.H. Chan School of Public Health.

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For more information, contact Hujoel at hujoel@uw.edu.

Researchers at the 天美影视传媒 have designed a convenient and natural product that uses proteins to rebuild tooth enamel and treat dental cavities.

The research finding was first published in .

鈥淩emineralization guided by peptides is a healthy alternative to current dental health care,鈥� said lead author , professor of materials science and engineering and adjunct professor in the Department of Chemical Engineering and Department of Oral Health Sciences.

The new biogenic dental products can 鈥� in theory 鈥� rebuild teeth and cure cavities without today鈥檚 costly and uncomfortable treatments.

鈥淧eptide-enabled formulations will be simple and would be implemented in over-the-counter or clinical products,鈥� Sarikaya said.

Cavities are more than just a nuisance. According to the , dental cavities affect nearly every age group and they are accompanied by serious health concerns. Additionally, direct and indirect costs of treating dental cavities and related diseases have been a huge economic burden for individuals and health care systems.

鈥淏acteria metabolize sugar and other fermentable carbohydrates in oral environments and acid, as a by-product, will demineralize the dental enamel,鈥� said co-author , associate professor in the Department of Restorative Dentistry at the UW School of Dentistry.

Although tooth decay is relatively harmless in its earliest stages, once the cavity progresses through the tooth鈥檚 enamel, serious health concerns arise. If left untreated, tooth decay can lead to tooth loss. This can present adverse consequences on the remaining teeth and supporting tissues and on the patient鈥檚 general health, including life-threating conditions.

Good oral hygiene is the best prevention, and over the past half-century, brushing and flossing have reduced significantly the impact of cavities for many Americans. Still, some socio-economic groups suffer disproportionately from this disease, the researchers said. And, according to recent reports from the , the prevalence of dental cavities in Americans is again on the rise, suggesting a regression in the progress of combating this disease.

Taking inspiration from the body鈥檚 own natural tooth-forming proteins, the UW team has come up with a way to repair the tooth enamel. The researchers accomplished this by capturing the essence of amelogenin 鈥� a protein crucial to forming the hard crown enamel 鈥� to design amelogenin-derived peptides that biomineralize and are the key active ingredient in the new technology. The bioinspired repair process restores the mineral structure found in native tooth enamel.

鈥淭hese peptides are proven to bind onto tooth surfaces and recruit calcium and phosphate ions,鈥� said Deniz Yucesoy, a co-author and a doctoral student at the UW.

The peptide-enabled technology allows the deposition of 10 to 50 micrometers of new enamel on the teeth after each use. Once fully developed, the technology can be used in both private and public health settings, in biomimetic toothpaste, gels, solutions and composites as a safe alternative to existing dental procedures and treatments. The technology enables people to rebuild and strengthen tooth enamel on a daily basis as part of a preventive dental care routine. It is expected to be safe for use by adults and children.

Co-authors are H. Fong, research scientist in the UW Department of Materials Science and Engineering, and , professor and chair of Orthodontics in the School of Dentistry.

The research was funded by the Washington State Life Sciences Discovery Fund and the UW Department of Restorative Dentistry鈥檚 Spencer Fund.

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For further information, contact sarikaya@uw.edu or .

But our tools for manipulating life 鈥� to treat disease, repair damaged tissue and replace lost limbs 鈥� come from the nonliving realm: metals, plastics and the like. Though these save and preserve lives, our synthetic treatments are rooted in a chemical language ill-suited to our organic elegance. Implanted electrodes scar, wires overheat and our bodies struggle against ill-fitting pumps, pipes or valves.

A solution lies in bridging this gap where artificial meets biological 鈥� harnessing biological rules to exchange information between the biochemistry of our bodies and the chemistry of our devices. In published Sept. 22 in , engineers at the 天美影视传媒 unveiled peptides 鈥� small proteins which carry out countless essential tasks in our cells 鈥� that can provide just such a link.

, led by UW professor in the Departments of Materials Science & Engineering, shows how a genetically engineered peptide can assemble into nanowires atop 2-D, solid surfaces that are just a single layer of atoms thick. These nanowire assemblages are critical because the peptides relay information across the bio/nano interface through molecular recognition 鈥� the same principles that underlie biochemical interactions such as an antibody binding to its specific antigen or protein binding to DNA.

Since this communication is two-way, with peptides understanding the “language” of technology and vice versa, their approach essentially enables a coherent bioelectronic interface.

“Bridging this divide would be the key to building the genetically engineered biomolecular solid-state devices of the future,” said Sarikaya, who is also a professor of chemical engineering and oral health sciences.

His team in the UW studies how to coopt the chemistry of life to synthesize materials with technologically significant physical, electronic and photonic properties. To Sarikaya, the biochemical “language” of life is a logical emulation.

“Nature must constantly make materials to do many of the same tasks we seek,” he said.

The UW team wants to find genetically engineered peptides with specific chemical and structural properties. They sought out a peptide that could interact with materials such as gold, titanium and even a mineral in bone and teeth. These could all form the basis of future biomedical and electro-optical devices. Their ideal peptide should also change the physical properties of synthetic materials and respond to that change. That way, it would transmit “information” from the synthetic material to other biomolecules 鈥� bridging the chemical divide between biology and technology.

In exploring the properties of 80 genetically selected peptides 鈥� which are not found in nature but have the same chemical components of all proteins 鈥� they discovered that one, GrBP5, showed promising interactions with the . They then tested GrBP5’s interactions with several 2-D nanomaterials which, Sarikaya said, “could serve as the metals or semiconductors of the future.”

“We needed to know the specific molecular interactions between this peptide and these inorganic solid surfaces,” he added.

Their experiments revealed that GrBP5 spontaneously organized into ordered nanowire patterns on graphene. With a few mutations, GrBP5 also altered the electrical conductivity of a graphene-based device, the first step toward transmitting electrical information from graphene to cells via peptides.

In parallel, Sarikaya’s team modified GrBP5 to produce similar results on a semiconductor material 鈥� molybdenum disulfide 鈥� by converting a chemical signal to an optical signal. They also computationally predicted how different arrangements of GrBP5 nanowires would affect the electrical conduction or optical signal of each material, showing additional potential within GrBP5’s physical properties.

“In a way, we’re at the flood gates,” said Sarikaya. “Now we need to explore the basic properties of this bridge and how we can modify it to permit the flow of ‘information’ from electronic and photonic devices to biological systems.”

This is the focus of a new endeavor funded by the National Science Foundation’s Materials Genome Initiative. It will be led by Sarikaya and joined by UW professors , and . Through UW’s , he is also working with Amazon to cross that bio/nano divide for nano-sensors to detect early stages of pancreatic cancer.

Lead author on the paper is former UW postdoctoral researcher , who is now an associate professor at the Tokyo Institute of Technology. Co-authors include two former UW researchers 鈥� , now with the Naval Research Laboratory, and Sefa Dag, now with IBM 鈥� as well as graduate students and . The research was funded by the NSF, the UW, the National Institutes of Health and the Japan Science and Technology Agency.

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For more information, contact Sarikaya at 206-543-0724 or sarikaya@uw.edu.

Grant numbers: DMR-0520567, T32CA138312, 25706012, DMR-1629071.