A new dental restoration composite more durable than the conventional material

Fewer trips to the dentist may be in your future, and you have mussels to thank.

Inspired by the mechanisms mussels use to adhere to inhospitable surfaces, UC Santa Barbara researchers have developed a new type of dental composite that provides an extra layer of durability to treated teeth. The potential payoff? Longer lasting fillings, crowns, implants and other work.
"It's as hard as a typical dental restoration but less likely to crack," Kollbe Ahn, a materials scientist at UCSB's Marine Science Institute, said of the composite. The research is highlighted in the journal Advanced Materials. The paper, of which Ahn is the corresponding author, is the result of collaboration between research and industry.

On average, a dental restoration lasts five to 10 or so years before needing replacement. The time frame depends on the type of restoration and how well the patient cares for the treated tooth. However, the continual onslaught of chewing, acidic and hard foods, poor hygiene, nighttime tooth grinding, generally weak teeth and even inadequate dental work can contribute to a filling's early demise -- and another expensive and possibly less-than-pleasant experience in the dental chair.

According to Ahn, one of the primary reasons restorations fall out or crack is brittle failure of the bond with the surrounding tooth. "All dental composites have micro-particles to increase their rigidity and prevent their shrinkage during their curing process," he explained. "But there's a trade-off: When the composite gets harder, it gets more brittle."

With enough pressure or wear and tear, a crack forms, which then propagates throughout the entire restoration. Or, the gap between the tooth and the restoration results in restoration failures, including marginal tooth decay.

So Ahn and his colleagues looked to nature -- mussels, to be exact -- to find a way not only to maintain strength and hardness but also to add durability. Having perfected the art of adhering to irregular surfaces under the variable conditions of the intertidal zone -- evolving to resist pounding waves, the blazing heat of the sun and cycles of salt water immersion and windy dryness -- mussels presented the ideal model for more durable dental restoration materials. The byssal threads they use to affix to surfaces allow them to resist the forces that would tear them from their moorings.

"In nature, the soft collagenous core of the mussel's byssal threads is protected by a 5-to-10 micrometer thick, hard coating, which is also extensible and thus, tough," Ahn said. This durability and flexibility allow the mollusks to stick to wet mineral surfaces in harsh environments that involve repeated push-and-pull stress.

Key to this mechanism is what the scientists call dynamic or sacrificial bonding -- multiple reversible and weak bonds on the sub-nanoscopic molecular level that can dissipate energy without compromising the overall adhesion and mechanical properties of the load-bearing material.

"Say you have one strong bond," Ahn explained. "It may be strong but once it breaks, it breaks. If you have several weaker bonds, you would have to break them one by one." Breaking each weak bond, he continued, would dissipate energy, so the overall energy required to break the material would be greater than with a single strong bond.

This type of bonding occurs in many biological systems, including animal bone and tooth. The mussel's byssus contain a high number of unique chemical functional groups called catechols, which are used to prime and promote adhesion to wet mineral surfaces. The new study shows that using a catecholic coupling agent instead of the conventional silane coupling agent provides 10 times higher adhesion and a 50 percent increase in toughness compared to current dental restorative resin composites.

While research has proven this toughening mechanism in soft materials, this study is one of the first -- if not the first -- to prove it with rigid and load-bearing materials.

This proof-of-concept, which also demonstrates no cytotoxicity, could mean tougher, more durable dental fillings. And that, in the long run, could mean fewer dental visits. Because each replacement filling also requires the dentist to file the surrounding tooth to prime its surface, given enough replacements a tooth might need to be crowned or extracted; and if not replaced, the tooth loss could have adverse consequences for the individual's diet and health.

The next step, Ahn said, is to increase the material's durability even further.

"By changing the molecular design you could have even denser coupling agents that exist on the surface, and then we can have a stronger and more durable dental composite," he said, estimating a commercial product within a couple of years.

Oral and Dental Problems That May Signal Child Abuse and Neglect

A report from the American Academy of Pediatrics and the American Academy of Pediatric Dentistry in the August 2017 Pediatrics (published online July 31) aims to help identify problems involving a child's teeth, gums and mouth that may be signs of physical or sexual abuse and neglect. According to the updated clinical report, "Oral and Dental Aspects of Child Abuse and Neglect," injuries and infections in and around the mouth appear often in children who are maltreated. These may occur when caregivers react violently during developmentally normal fussiness at mealtime or bedtime, for example.

Symptoms that may be signs of child abuse or neglect include:

• bruises on the lips, gums, tongue, lips or soft tissue inside the mouth from eating utensils or a bottle during forced feeding;
• burns or blisters from scalding liquids or fractures to teeth, facial or jaw bones or scars or blackened teeth from previous injuries;
• skin irritation, bruising or scarring at the corners of the mouth, which could be from gags applied to the mouth in forceful attempts to quiet a child;
• injuries to the back of the throat, sometimes intentionally inflicted to make a child cough up or vomit blood or create other symptoms that would require medical attention and care;
• injuries and infections tied to forced oral sex, such as tears and other signs of trauma inside the mouth or sores or rashes caused by sexually transmitted disease.
• bite marks inside the mouth from the child's own teeth, which sometimes are caused by physical or sexual abuse.

In cases of dental neglect, authors note, untreated cavities and gum disease interfere with a child's ability to eat, communicate, grow and develop properly. The report also describes the connection between bullying and dental health, citing research indicating that children with mouth or dental abnormalities are frequent targets of bullying and face increased risk of depression and suicidal thoughts or actions.

In addition, the estimated 100,000 U.S. children involved in sex trafficking or forced prostitution each year have oral and dental problems from abuse and from malnutrition, which can lead to poorly formed teeth, cavities, infections and tooth loss.

Chewing gum rapid test for inflammation

Dental implants occasionally entail complications: Six to fifteen percent of patients develop an inflammatory response in the years after receiving a dental implant. This is caused by bacteria destroying the soft tissue and the bone around the implant in the worst case.
In future, patients will benefit from a quick and affordable method assessing whether they carry such bacteria: using a chewing gum based diagnostic test developed by a pharmaceutical research team at the Julius-Maximilians-Universität (JMU) Würzburg in Bavaria, Germany.

In practice, the test works as follows: If there is an inflammation in the oral cavity, a bittering agent is released while chewing the gum. Patients can then visit their dentist who confirms the diagnosis and treats the disease. This type of early detection aims at preventing serious complications such as bone loss.

"Anyone can use this new diagnostic tool anywhere and anytime without any technical equipment," Professor Lorenz Meinel says; he is the head of the JMU Chair for Drug Formulation and Delivery. He developed the new diagnostic tool with Dr. Jennifer Ritzer and her team; the invention is currently featured in an article in the journal Nature Communications.

Enzymes release bitter taste
The scientific background: In the presence of inflammatory conditions, specific protein-degrading enzymes are activated in the mouth. In just five minutes, these enzymes also break down a special ingredient of the chewing gum, thereby releasing a bittering agent that could not be tasted before.
Meinel's team provided the proof that this principle actually works. First studies using the saliva of patients were conducted at Merli Dental Clinic in Rimini.

Company establishment planned
To launch the chewing gum into the market, Meinel's team plans to set up a company. The professor assumes that it will take two to three years until the gum is commercially available.
Chewing gum rapid tests for other medical applications are presently under development. "We hope to be able to diagnose other diseases with our "anyone, anywhere, anytime" diagnostics to identify and adress these diseases as early as possible," Meinel explains.

High sugar consumption gives rise to dental treatment costs in the billions

Worldwide, people are eating far too much sugar. This has negative consequences for their teeth and for their purses: seen at the global level, the costs of dental treatment are currently running at around 172 billion US dollars (128 billion euros). In Germany alone, these amount to 17.2 billion euros (23 billion US dollars) a year. These are the results of a joint study conducted by the Martin Luther University Halle-Wittenberg (MLU) and the Biotechnology Research and Information Network AG (BRAIN AG) published in the International Journal of Dental Research. The work was carried out within the strategic alliance NatLifE 2020 and was co-financed by the German Federal Ministry of Education and Research (BMBF).

For their work the researchers evaluated representative data on the prevalence of caries, inflammation of the gums (parodontitis) and tooth loss, corresponding costs of treatment and the disease burden, as well as data on sugar consumption, in 168 countries for the year 2010. On the basis of this data they calculated the share of total costs attributable to excessive consumption of sugar. In addition to white household sugar, the researchers also focused their attention, in the analysis, to "hidden" sugar that is contained in many processed products, such as soft drinks, ketchup, ice cream and frozen foods, as well as breads, cakes and pastries.

"The data shows a clear correlation between the consumption of sugar and the incidence of caries, parodontitis and, as a result, tooth loss," said the lead author of the study, Dr Toni Meier from the Institute of Agricultural and Nutritional Sciences at the MLU. "For every additional 25 grams of sugar consumed per person and day - which amounts to roughly eight sugar-cubes or a glass of sweetened lemonade - the costs of dental treatment in high-income countries increase on average by 100 US dollars (75 euros) per person and year."

In Germany, the average daily sugar consumption lies between 90 and 110 grams per person. The costs of treatment amount to 281 US dollars (210 euros) per person and year. This puts Germany in the group of countries with the highest costs of treatment per person and year. Other countries "in the group" are Switzerland (402 US dollars, 300 euros), Denmark (238 US dollars, 178 euros) and the USA (185 US dollars, 138 euros). "If the target of 50 grams of sugar per person and day set by the World Health Organization could be reached, this would result in savings in the costs of treatment within Germany of 150 euros (201 US dollars) per person and year. Extrapolating this figure to the federal level shows annual potential savings of approximately 12 billion euros, or 16 billion US dollars," added Meier. A low-sugar diet is becoming increasingly difficult, however, since almost all processed products in the supermarket contain large quantities of added sugars.

The highest levels of sugar-related dental illness were observed by the researchers in Guatemala, Mauretania and Mexico. "Newly industrialised countries such as India, Brazil and Mexico, but also Pakistan and Egypt, could avoid an excessive burden of illness and of health care costs by anchoring the topic in their health and nutritional policies at an early stage," said the co-author of the study and nutrition scientist, Professor Gabriele Stangl of the MLU. This objective could be achieved by way of educational campaigns or by special taxation on high-calorie food. Such a sugar tax was introduced in Mexico in 2014 and already after one year was proving to be effective: the consumption of sugar-sweetened beverages had decreased by five percent. In the second year this decrease even doubled to ten percent.

"To be able to reduce the burden of nutrition-related illnesses, a balanced mix of educational work and food-policy initiatives, along with innovative technological solutions, are needed," said the co-author of the study, Dr Katja Riedel, joint coordinator of the NatLifE 2020 innovative alliance and program manager of system-products nutrition at BRAIN AG. The alliance co-financed by the German Federal Ministry of Education and Research aims, with the help of biotechnology and the understanding of biological systems, to develop a new generation of sustainably produced and biological active substances for foods and cosmetics and thereby to make a contribution towards improving human nutrition, health and well-being.

Man loses feeling in legs after long-term denture fixative use

A 62-year-old man lost the feeling in both his legs after the regular long term use of a denture fixative containing zinc, reveal doctors writing in the online journal BMJ Case Reports.

The man was referred to a neurology clinic after developing numbness, pain and weakness in his legs. The symptoms, which had lasted for more than six months, stopped him from leaving the house.
An MRI (magnetic resonance imaging) scan revealed spinal cord abnormalities and after several tests he was diagnosed with copper deficiency myelopathy (CDM).

CMD is a neurological disorder which can cause loss of feeling and numbness in the arms and legs.
The man explained that he had been using 2-4 tubes of denture fixative that contained zinc every week for the past 15 years because of his ill-fitting false teeth.

Excess zinc intake can interfere with the absorption of copper, leading to neurological problems, in rare cases.

The man was advised to stop using the fixative and given copper supplements to treat his symptoms. But he didn't recover completely, and the doctors warn that irreversible nerve damage may be a consequence of a delayed diagnosis of CDM.

An end to cavities for people with sensitive teeth?

An ice cold drink is refreshing in the summer, but for people with sensitive teeth, it can cause a painful jolt in the mouth. This condition can be treated, but many current approaches don't last long. Now researchers report in the journal ACS Applied Materials & Interfaces the development of a new material with an extract from green tea that could fix this problem -- and help prevent cavities in these susceptible patients.  

Tooth sensitivity commonly occurs when the protective layers of teeth are worn away, revealing a bony tissue called dentin. This tissue contains microscopic hollow tubes that, when exposed, allow hot and cold liquids and food to contact the underlying nerve endings in the teeth, causing pain. Unprotected dentin is also vulnerable to cavity formation. Plugging these tubes with a mineral called nanohydroxyapatite is a long-standing approach to treating sensitivity. But the material doesn't stand up well to regular brushing, grinding, erosion or acid produced by cavity-causing bacteria. Cui Huang and colleagues wanted to tackle sensitivity and beat the bacteria at the same time.

The researchers encapsulated nanohydroxyapatite and a green tea polyphenol -- epigallocatechin-3-gallate, or EGCG -- in silica nanoparticles, which can stand up to acid and wear and tear. EGCG has been shown in previous studies to fight Streptococcus mutans, which forms biofilms that cause cavities. Testing on extracted wisdom teeth showed that the material plugged the dentin tubules, released EGCG for at least 96 hours, stood up to tooth erosion and brushing and prevented biofilm formation. It also showed low toxicity. Based on these findings, the researchers say the mate

History of gum disease increases cancer risk in older women

Postmenopausal women who have a history of gum disease also have a higher risk of cancer, according to a new study of more than 65,000 women.

The study, led by researchers at the University at Buffalo, is the first national study of its kind involving U.S. women, and the first to focus specifically on older women. It's also the first study to find an association between periodontal disease and gallbladder cancer risk in women or men. The findings were published today (Aug. 1) in the journal Cancer Epidemiology, Biomarkers & Prevention.

"This study is the first national study focused on women, particularly older women," said Jean Wactawski-Wende, the study's senior author.

"Our study was sufficiently large and detailed enough to examine not just overall risk of cancer among older women with periodontal disease, but also to provide useful information on a number of cancer-specific sites," added Wactawski-Wende, dean of UB's School of Public Health and Health Professions and a professor of epidemiology and environmental health.

The study included 65,869 postmenopausal women enrolled in the Women's Health Initiative, an ongoing national prospective study designed to investigate factors affecting disease and death risk in older American women. The average age of the participants was 68, and most were non-Hispanic white women.

As part of a follow-up health questionnaire, participants were asked "Has a dentist or dental hygienist ever told you that you had periodontal or gum disease?"

Women who reported a history of gum disease had a 14 percent increased risk of overall cancer. Of the 7,149 cancers that occurred in the study participants, the majority -- or 2,416 -- were breast cancer.

"There is increasing evidence that periodontal disease may be linked to an increased cancer risk and this association warrants further investigation," said the paper's first author, Ngozi Nwizu, who worked on the research while completing her residency in oral and maxillofacial pathology in UB's School of Dental Medicine and her doctorate in pathology (cancer epidemiology) at UB's Roswell Park Cancer Institute Graduate Division. Nwizu is now an assistant professor of oral and maxillofacial pathology at the University of Texas Health Science Center at Houston.

The risk associated with periodontal disease was highest for esophageal cancer, the researchers reported. "The esophagus is in close proximity to the oral cavity, and so periodontal pathogens may more easily gain access to and infect the esophageal mucosa and promote cancer risk at that site," Wactawski-Wende said.

Gallbladder cancer risk also was high in women who reported a history of gum disease. "Chronic inflammation has also been implicated in gallbladder cancer, but there has been no data on the association between periodontal disease and gallbladder risk. Ours is the first study to report on such an association," Nwizu said.

The esophageal and gallbladder cancer findings are significant, Nwizu said. "Esophageal cancer ranks among the most deadly cancers and its etiology is not well known, but chronic inflammation has been implicated," she said.

"Certain periodontal bacteria have been shown to promote inflammation even in tiny amounts, and these bacteria have been isolated from many organ systems and some cancers including esophageal cancers. It is important to establish if periodontal disease is an important risk of esophageal cancer, so that appropriate preventive measures can be promoted."

Periodontal disease also was associated with total cancer risk among former and current smokers.
The findings for this particular age group are significant because they offer a window into disease in a population of Americans that continues to increase as people live longer lives.

"The elderly are more disproportionately affected by periodontal disease than other age groups, and for most types of cancers, the process of carcinogenesis usually occurs over many years," said Nwizu. "So the adverse effects of periodontal disease are more likely to be seen among postmenopausal women, simply because of their older age."