Dental Products: Sensor Detects Bad Breath

Half of all adults have suffered from bad breath or halitosis at some point in their lives, says the American Dental Association. Although in most cases bad breath is simply an annoyance, it can sometimes be a symptom of more serious medical and dental problems. However, many people aren't aware that their breath is smelly unless somebody tells them, and doctors don't have a convenient, objective test for diagnosing halitosis.

Researchers - reporting in ACS' journal Analytical Chemistry - have developed a sensor that detects tiny amounts of hydrogen sulfide gas - the compound responsible for bad breath - in human exhalations. Existing hydrogen sulfide sensors require a power source or precise calibration or they show low sensitivity or a slow response.

The researchers wanted to develop a sensitive, portable detector for halitosis that doctors could use to quickly and inexpensively diagnose the condition. They made use of lead acetate, which turns brown when exposed to hydrogen sulfide gas. The chemical on its own is not sensitive enough to detect trace amounts of hydrogen sulfide in human breath so the researchers anchored lead acetate to a 3D nanofiber web, providing numerous sites for lead acetate and hydrogen sulfide gas to react. By monitoring a color change from white to brown on the sensor surface, the researchers could detect as little as 400 ppb (parts per billion) hydrogen sulfide with the naked eye in only one minute. In addition, the color-changing sensor detected traces of hydrogen sulfide added to breath samples from 10 healthy volunteers.

Peptide-Based Biogenic Dental Product May Cure Cavities

Tooth decay is relatively harmless in its earliest stages, but once the cavity progresses through the tooth’s 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’s general health, including life-threading 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. Additionally, recent reports from the Centers for Disease Control and Prevention say the prevalence of dental cavities in Americans is again on the rise, suggesting a regression in the progress of combating this disease.

Researchers at the University of Washington recently designed a convenient and natural product that uses proteins to rebuild tooth enamel and treat dental cavities. The research was published in ACS Biomaterials Science and Engineering. “Remineralization guided by peptides is a healthy alternative to current dental health care,” says lead author Mehmet Sarikaya, professor of materials science and engineering and adjunct professor in the Department of Chemical Engineering and Department of Oral Health Sciences.

The biogenic dental products can in theory rebuild teeth and cure cavities without today’s costly and uncomfortable treatments. “Peptide-enabled formulations will be simple and would be implemented in over-the-counter or clinical products,” Sarikaya added. Dental cavities affect nearly every age group and they are accompanied by serious health concerns, according to the World Health Organization. Direct and indirect costs of treating dental cavities and related diseases have been a huge economic burden for individuals and health care systems. “Bacteria metabolize sugar and other fermentable carbohydrates in oral environments and acid, as a by-product, will demineralize the dental enamel,” added co-author Sami Dogan, associate professor in the Department of Restorative Dentistry at the UW School of Dentistry.

The researchers came up with a way to repair the tooth enamel by capturing the essence of amelogenin - a protein crucial to forming the hard crown enamel - to design amelogenin-derived peptides that biomineralize and are the key active ingredient in the new technology. The bio-inspired repair process restores the mineral structure found in native tooth enamel. “These peptides are proven to bind onto tooth surfaces and recruit calcium and phosphate ions,” says 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.

Polymer Bacteria Fighter

Clear aligners or retainers, known collectively as clear overlay appliances (COAs) are made by taking a dental cast and using pressure or heat on a plastic sheet. But bacteria frequently build up on COAs as difficult-to-treat biofilms, and the plastics easily wear down. Scientists have turned to developing simple and affordable coatings to combat this. Researchers have developed a film to prevent bacteria from growing on plastic aligners and retainers as reported in ACS Applied Materials & Interfaces.

The researchers took a polymer sheet made of polyethylene terephthalate that was modified with glycol (PETG) and layered films of carboxymethylcellulose and chitosan. This layered film created a super-hydrophilic surface, or a surface that loves water, that prevented bacteria from adhering. When PETG with the film was compared to the bare material, bacterial growth was reduced by 75 percent. The coated plastic also was stronger and more durable, even when tested with artificial saliva and various acidic solutions.

Adhesives Prevent Bracket Stains On Teeth

CEU UCH Odontology researchers from Valencia, Spain; London, England; and Sul, Brazil performed research to develop adhesive materials that will prevent white stains from appearing on the teeth of people who use brackets. The white stains that orthodontic brackets often leave on teeth is a result of enamel demineralization caused by bacterial proliferation in the adhesive area, especially when accompanied by inadequate oral hygiene. Researchers at the Odontology Department of Valencia’s Universidad CEU Cardenal Herrera in collaboration with the King’s College London Dental Institute and the Universidade Federaldo Rio Grande do Sul in Brazil have compared the efficacy of three types of experimental adhesives with bactericidal and enamel remineralization properties which could prevent the appearance of these white stains around the brackets.

The study – published in the Journal of Dentistry - compares three experimental dental adhesives which contain a bioactive nano-mineral called halloysite and whose nanotubes have been loaded with triclosan, a strong antibacterial and fungicidal agent in different concentrations: 5, 10 and 20 percent. The research compares the three new, experimental biomaterials’ polymerization properties, their antibacterial strength and bioactive properties, which not only prevent demineralization of the teeth, but also promote remineralization.

The three experimental materials tested in the laboratory have demonstrated an ability to stop bacterial proliferation in the 24 hours following their use, but only the one with the highest concentration of triclosan, at 20 percent, has maintained this property after 72 hours. As far as the remineralizing effect, all three tested materials have proven to be effective two weeks after their use in dental enamel samples submerged in experimental saliva. These results are a promising step forward in the development of new adhesives that are capable of preventing the appearance of the bacteria that demineralize the enamel surrounding the brackets and, at the same time, remineralize the area and thus prevent the appearance of white stains on the teeth.

A Dental Material That Resists Plaque And Kills Microbes

Researchers from the University of Pennsylvania recently evaluated a new dental material tethered with an antimicrobial compound that can not only kill bacteria but can also resist biofilm growth. The study was published in the journal ACS Applied Materials and Interfaces.

Dentists rely on composite materials to perform restorative procedures, such as filling cavities. Yet these materials, like tooth enamel, can be vulnerable to the growth of plaque, the sticky biofilm that leads to tooth decay. In addition, unlike some drug-infused materials, it is effective with minimal toxicity to the surrounding tissue, as it contains a low dose of the antimicrobial agent that kills only the bacteria that come in contact with it. "Dental biomaterials such as these need to achieve two goals: first, they should kill pathogenic microbes effectively, and, second, they need to withstand severe mechanical stress, as happens when we bite and chew,” says Geelsu Hwang, research assistant professor in Penn's School of Dental Medicine. “Many products need large amounts of anti-microbial agents to maximize killing efficacy, which can weaken the mechanical properties and be toxic to tissues, but we showed that this material has outstanding mechanical properties and long-lasting antibiofilm activities without cytotoxicity."

The material is composed of a resin embedded with the antibacterial agent imidazolium. Unlike some traditional biomaterials, which slowly release a drug, this material is non-leachable, thereby only killing microbes that touch it. "This can reduce the likelihood of antimicrobial resistance," Hwang added.  The researchers put the material through its paces, testing its ability to kill microbes, to prevent growth of biofilms and to withstand mechanical stress. Their results showed it to be effective in killing bacterial cells on contact, severely disrupting the ability of biofilms to grow on its surface. Only negligible amounts of biofilm matrix, the glue that holds clusters of bacteria together, were able to accumulate on the experimental material, in contrast to a control composite material, which showed a steady accumulation of sticky biofilm matrix over time. Then, the team assessed how much shear force was required to remove the biofilm on the experimental material.

While the smallest force removed almost all the biofilm from the experimental material, even a force four times as strong was incapable of removing the biofilm from the control composite material. "The force equivalent to taking a drink of water could easily remove the biofilm from this material," Hwang said.


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