The fight against tooth decay gets help with a new smart material

When patients go to the dentist to fill a cavity, they're trying to solve a problem -- not create a new one. But many dental patients get some bad news: bacteria can dig under their tooth-coloured fillings and cause new cavities, called recurrent caries. These recurrent caries affect 100 million patients every year and cost an additional US$34 billion to treat.

Now, a research collaboration between the Department of Materials Science & Engineering, Faculty of Dentistry, and the Institute of Biomaterials and Biomedical Engineering at the University of Toronto has resulted in a novel way to minimize recurrent caries.

In a recent paper published in the journal Scientific Reports, professors Ben Hatton, Yoav Finer and PhD student Cameron Stewart tackled the issue and proposed a novel solution: a filling material with tiny particles made by self-assembly of antimicrobial drugs, designed to stop bacteria in its tracks. These particles may solve one of the biggest problems with antibacterial filling materials: how do you store enough drug within the material to be effective for someone's entire life?

"Adding particles packed with antimicrobial drugs to a filling creates a line of defense against cavity-causing bacteria," says Hatton. "But traditionally there's only been enough drug to last a few weeks. Through this research we discovered a combination of drugs and silica glass that organize themselves on a molecule-by-molecule basis to maximize drug density, with enough supply to last years." This discovery of using antimicrobials which self-assemble means the team can pack 50 times as much of the bacteria-fighting drugs into the particles.

"We know very well that bacteria specifically attack the margins between fillings and the remaining tooth to create cavities," says Finer. "Giving these materials an antimicrobial supply that will last for years could greatly reduce this problem."

Looking ahead, the research team plans on testing these new drug-storing particles in dental fillings, monitoring their performance when attacked by bacteria and saliva in the complex environment in the mouth. With some fine-tuning, this new 'smart' material could create a stronger filling and fewer trips to the dentist.

Adhesives developed to prevent bracket stains on teeth

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Researchers from Valencia (Spain), London (England) and Sul (Brazil) have 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, specially 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 (Brazil) have compared the efficacy of three new types of experimental adhesives, with bactericidal and enamel remineralisation properties which could prevent the appearance of these white stains around the brackets.

The research has been published in the Journal of Dentistry scientific magazine, one of the most prestigious in the field on an international level.

Bactericidal and remineralisation properties

The study 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 per cent. The research compares the three new, experimental biomaterials’ polymerisation properties, their antibacterial strength and bioactive properties, which not only prevent demineralization of the teeth, but also promote remineralisation.

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 per cent, has maintained this property after 72 hours. As far as the remineralising 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 demineralise the enamel surrounding the brackets and, at the same time, remineralise the area and thus prevent the appearance of white stains on the teeth.
 

 

Cavity prevention approach effectively reduces tooth decay

A scientifically based approach that includes a tooth-decay risk assessment, aggressive preventive measures and conservative restorations can dramatically reduce decay in community dental practices, according to a study by researchers at UC San Francisco.

The findings, which support earlier research demonstrating positive results of the assessment and treatment method in a university setting, have the potential to transform dental care for high-risk patients at a lower cost to both patients and dental clinics and practices. Results appear online Jan. 22, 2018, in Advances in Dental Research.

"We put the 2012 UCSF clinical study into the real world and showed it works," said lead author Peter Rechmann, DMD, PhD, professor of preventive and restorative dental sciences in the UCSF School of Dentistry. "The patients at high caries risk who used prescription products went down significantly over time in their risk level. Those in the control group also reduced their risk to a lesser degree, simply by using over-the-counter products that also protect teeth and affect the bacteria."

Dental caries (tooth decay) is caused by bacteria on the tooth surface feeding on carbohydrates, then making acids as waste. These acids destroy the protective tooth enamel and the dentin layer beneath it. If not halted or reversed, this leads to a cavity.

CAries Management By Risk Assessment (CAMBRA?) is an evidence-based approach to preventing or treating dental caries at its earliest stages. It was launched in 2003 through the UCSF School of Dentistry by the paper's senior author, John Featherstone, PhD, MSc, former dean of the school and distinguished professor of preventive and restorative dental sciences.

A dentist who uses CAMBRA obtains the patient's dental and medical history and conducts a clinical exam to assess caries early enough to reverse or halt progression and to determine caries risk factors. These factors include, among other things, acid-producing bacteria, frequent eating and drinking of fermentable carbohydrates ("snacking"), and abnormally low saliva flow and function.

From this assessment, the dentist utilizes behavioral approaches and chemical treatments to optimize protective factors. The treatment plan typically incorporates remineralization through the use of fluoride and/or antibacterial therapies such as chlorhexidine and xylitol, minimally invasive restorative procedures to conserve tooth structure, and regular patient follow up.

The authors published their initial validation of CAMBRA for ages 6 through adult in 2006, followed by several additional years of data published in 2011, 2012, 2015 and 2016. Since then, more than half of the U.S. schools and colleges of dentistry have adopted CAMBRA in one form or another as part of their standard curriculum. The authors said now that this has been shown to be effective in a non-academic clinical setting, there also is potential for insurance companies to reimburse CAMBRA and other preventive therapies for adults, thereby lowering patient costs while increasing profits for dental practices.
Treatment Effective Even Without Prescription Products

In the Advances in Dental Research study, Rechmann and his colleagues recruited 20 dentists - 17 in private practice, three in community clinics - to participate in a two-year CAMBRA trial of 460 patients ages 12-65 years old, with 239 in a CAMBRA group and 221 in a control group.
In the CAMBRA group, high-risk patients received prescription fluoride toothpaste, chlorhexidine antibacterial rinse, xylitol mints and fluoride varnish. The control group received regular fluoride toothpaste, an assumed inactive mouth rinse, sorbitol candies and a non-fluoride varnish.

Follow-up visits occurred at six, 12, 18 and 24 months, in which new caries lesions or changes in caries risk level were recorded. Overall, the researchers found that a significantly greater percentage of high-risk participants were classified at lower risk after receiving CAMBRA preventive therapies. Dental decay was low in both groups.

Among 242 patients (137 intervention, 105 control) initially identified as high risk for caries, only a quarter of the patients remained at high risk in the CAMBRA group at 24 months, while just over half (54 percent) of the control group did. Of the 192 low-risk participants (93 intervention, 99 control), most participants remained low risk, indicating that the assessment correctly identifies who is at risk for caries.

The researchers said the risk reduction among the control group may have been caused by the fluoride toothpaste enhancing tooth repair, as well as the mouth rinse enhancing saliva flow and having bactericidal effects. While not as significant as the CAMBRA group in this study, the risk level of these patients dropped more dramatically over time than for those in the 2012 UCSF CAMBRA study.

"It was surprising to see the benefits gained by the control group," Rechmann said. "More research is needed to see if the products and treatment administered to this group function in the way we speculate, and if so, they might be made easily available to dental patients. Doing so can change the whole picture of caries control."

Among the study limitations, the researchers noted a high study attrition (65 percent), which partly may have contributed to observed declines in risk level at each subsequent recall visit.

Blasting dental plaque with microbubbles

IMAGE: The researchers used a certain type of nozzle to create the cavitation bubbles which removed the plaque when they collapsed. view more 

Credit: Hitoshi Soyama

Whether through an accident or a disease, teeth loss can cause many inconveniences. Dental implants such as crowns, however, have allowed people to overcome most of these and live a better quality of life.

But just like normal teeth, these dental implants require proper care and oral hygiene to prevent further complications, such as the inflammation of the tissues surrounding the implants. While the buildup of dental plaque sticks mainly to the crown, it also adheres to the exposed parts of the screw that holds the dental fixture in place, and these are much harder to clean because they contain microgrooves that make them fit better into the upper or lower jaw bones.

Hitoshi Soyama from Tohoku University and his team from Showa University in Japan conducted a study to look for better ways for dentists to remove this plaque and prevent complications. The team wanted to study the efficiency of a cavitating jet, where high-speed fluid is injected by a nozzle through water to create very tiny bubbles of vapour. When these bubbles collapse, they produce strong shockwaves that are able to remove contaminants.

The team compared the cleaning effect of a cavitating jet to that of a water jet, which has been used for a long time to remove plaque from dental implants to keep them clean. They grew a biofilm over three days within the mouths of four volunteers, then proceeded to clean that with the two different methods, measuring the amount of plaque remaining at several time intervals.

While there was little difference between the amounts of dental plaque removed by both methods after one minute of cleaning, that changed after longer exposure. After three minutes, the cavitating jet had removed about a third more plaque than the water jet did, leaving little plaque stuck to the implant at the end of the experiment. The cavitating jet was also able to remove the plaque not only from the root section of the screws, but also from the harder-to-reach crest section, though to a lesser extent.

"Conventional methods cannot clean plaques on the surface of dental implants very well, so this new method could give dentists a new tool to better manage these fixtures which are becoming more common," says Soyama.

Previous research has shown that water flow exerts shear stress to remove the biofilm. In addition to this shear effect, the cavitating jet also produces a considerable force when the bubbles collapse that is able to remove particles from the biofilm and carry them away. The researchers suggest that the two processes probably work in synergy to make the cavitating jet superior to the water jet when cleaning the plaque off the irregular surface of dental implants.

Oral health may have an important role in cancer prevention

Researchers at the University of Helsinki and the Helsinki University Hospital, Finland, and the Karolinska Institutet, Sweden, have investigated the role of bacteria causing periodontitis, an inflammation of the tissues surrounding the teeth, in the development of oral cancers and certain other cancers, as well as the link between periodontitis and cancer mortality on the population level.
The study, published in the British Journal of Cancer, has for the first time proven the existence of a mechanism on the molecular level through which the bacteria associated with periodontitis, Treponema denticola (Td), may also have an effect on the onset of cancer.

Researchers found that the primary virulence factor of the Td bacteria, the Td-CTLP proteinase (an enzyme), occurs also in malignant tumours of the gastrointestinal tract, for example, in pancreatic cancer.

According to another study finding, the CTLP enzyme has the ability to activate the enzymes that cancer cells use to invade healthy tissue (pro-MMP-8 and -9). At the same time, CTLP also diminished the effectiveness of the immune system by, for example, inactivating molecules known as enzyme inhibitors.

In another study, published in the International Journal of Cancer, it was proven that on the population level, periodontitis is clearly linked with cancer mortality. An especially strong link to mortality caused by pancreatic cancer was found. Some 70,000 Finns took part in this 10-year follow-up study.

"These studies have demonstrated for the first time that the virulence factors of the central pathogenic bacteria underlying gum disease are able to spread from the mouth to other parts of the body, most likely in conjunction with the bacteria, and take part in central mechanisms of tissue destruction related to cancer," says Dr. Timo Sorsa, a professor at the University of Helsinki.

Researchers have come to the conclusion that a low-grade systemic inflammation related to periodontitis facilitates the spreading of oral bacteria and their virulence factors to other parts of the body. They point out that the prevention and early diagnosis of periodontitis are very important not only for patients' oral health, but their overall wellbeing.

"In the long run, this is extremely cost-effective for society," notes Sorsa.

More evidence of link between severe gum disease and cancer risk

Data collected during a long-term health study provides additional evidence for a link between increased risk of cancer in individuals with advanced gum disease, according to a new collaborative study led by epidemiologists Dominique Michaud at Tufts University School of Medicine and Elizabeth Platz of the Johns Hopkins Bloomberg School of Public Health and Kimmel Cancer Center.

The study, published in the Journal of the National Cancer Institute, used data from comprehensive dental exams performed on 7,466 participants from Maryland, Minnesota, Mississippi, and North Carolina, as part of their participation in the Atherosclerosis Risk in Communities (ARIC) study who were then followed from the late 1990s until 2012. During the follow-up period, 1,648 new cancer cases were diagnosed.

The research team found a 24 percent increase in the risk of developing cancer among participants with severe periodontitis, compared to those with mild to no periodontitis at baseline. Among patients who had no teeth-- which can be a sign of severe periodontitis -- the increase in risk was 28 percent.

The highest risk was observed in cases of lung cancer, followed by colorectal cancer.

When the researchers did sub-group analyses, they found that participants with severe periodontal disease had more than double the risk of developing lung cancer, compared with no/mild periodontitis. An 80 percent increase in risk of colon cancer observed for participants who were edentulous at baseline, which is consistent with prior findings, and among never smokers, a two-fold higher risk was noted for participants with severe periodontitis, compared to those who had no/mild periodontitis.

"This is the largest study addressing the association of gum disease and cancer risk using dental examinations to measure gum disease prior to cancer diagnosis," said first and corresponding author Dominique Michaud, Sc.D., professor of public health and community medicine at Tufts University School of Medicine. "Additional research is needed to evaluate if periodontal disease prevention and treatment could help alleviate the incidence of cancer and reduce the number of deaths due to certain types of cancer."

Michaud noted that the findings were particularly interesting in light of research, including a recent study in Science, which determined that colorectal cancer tissues contain bacteria that are present in the mouth, including bacteria that have been associated with periodontal disease.

The researchers also uncovered a small increase in the risk of pancreatic cancer in patients with severe periodontitis. Although not significant statistically, the association has been seen in other similar studies, including a number of studies led by Michaud of Tufts.

The research team accounted for the impact of smoking among the participants, since people who smoke are more likely to get periodontal disease, and smoking raises the risk of lung and colon cancers.

"When we looked at data for the people who had never smoked, we also found evidence that having severe periodontal disease was related to an increased risk of lung cancer and colorectal cancer," said Elizabeth Platz, Sc.D., deputy chair of the department of epidemiology at the Johns Hopkins Bloomberg School of Public Health and co-leader of the Cancer Prevention and Control Program at the Johns Hopkins Kimmel Cancer Center.

The ARIC data were especially useful to study because unlike most previous research linking gum disease and cancer risk, periodontitis cases were determined from dental examinations performed as part of the ARIC study rather than participants' self-reports of the disease. The dental exams provided detailed measurements of the depth of the pocket between the gum and tooth in several locations in the mouth. The ARIC data include both Caucasian and African-American participants.

The researchers found no links between increased risk of breast, prostate or blood/lymphatic cancer and periodontitis. The link between periodontitis and increased cancer risk was weaker or not apparent in African-American participants from the ARIC study, except in cases of lung and colorectal cancer. "Additional research is needed to understand cancer-site specific and racial differences in findings," wrote the authors. The researchers caution that the study was limited in size for subgroup analyses, and less common cancers. The findings, however, suggest the need for further study.

Michaud and Platz said the study also points to the importance of expanding dental insurance to more individuals. "Knowing more about the risks that come about with periodontal disease might give more support to having dental insurance in the way that we should be offering health insurance to everyone," Platz said.

Advanced gum disease, also called periodontitis, is caused by bacterial infection that damages the soft tissue and bone that support the teeth. Previous research has shown a link between periodontitis and increased cancer risk, although the mechanism connecting the two diseases is still uncertain.

Poor dental health increases risks of frailty in older men

Oral health issues are common among older adults. These issues include tooth loss, gum disease, tooth decay, and dry mouth. These conditions can also affect an older adult's well-being because they may make it harder to eat, swallow, speak, get adequate nutrition, and even smile.
Oral health issues like tooth loss and gum disease are also linked to increased risks of frailty. Frailty is the medical term for becoming more vulnerable to declining health or the inability to perform the activities of daily living. Frailty is a major healthcare challenge for older adults and caregivers. Someone who is frail can be weak, have less endurance, and be less able to function well. Frailty increases the risk for falls, disability, and even death.
Over a three-year period, researchers from the United Kingdom examined the relationship between poor oral health and older adults' risks for becoming frail. They published their findings in the Journal of the American Geriatrics Society.
The researchers studied information from the British Regional Heart Study. This study included 7,735 British men. They were first examined in 1978 to 1980 when they were 40- to 59-years-old. In 2010 to 2012, researchers invited 1,722 surviving participants to be re-examined. During that time period, the participants were 71- to 92-years-old.
Participants were given physical exams, which included height, weight, and waist measurements. They also took timed walking tests and had their grip strength measured. They answered questions about their medical history and lifestyle. They also answered a questionnaire asking about medical, social, and health-related information.
The exam included a dental exam. Dental health professionals counted the participants' natural teeth and measured the health of their gums. Participants answered questions about their dental health, including if they had dry mouth.
Researchers also noted the participants' frailty status. Participants were considered frail if they had at least three of these issues: exhaustion, weak grip strength, slow walking speed, weight loss, or low levels of physical activity.
The researchers found out the following facts about the participants' dental issues:

• 20 percent had no teeth
• 64 percent had fewer than 21 teeth
• 54 percent had gum disease
• 29 percent had at least two symptoms of dry mouth
• 34 percent rated their oral health as "fair to poor"
• 11 percent said they had trouble eating

The researchers said that men with dental issues were more likely to be frail than men without those issues. These dental issues included having no teeth, having trouble eating, having dry mouth symptoms, or rating oral health as "fair to poor."
The researchers also noted that complete tooth loss, dry mouth, and additional oral health concerns were especially linked to developing frailty.
The researchers concluded that these findings highlight the importance of oral health for older adults, suggesting that poor oral health contributes to frailty.

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This summary is from "Influence of poor oral health on physical frailty: a population-based cohort study of older British men". It appears online ahead of print in the Journal of the American Geriatrics Society. The study authors are Sheena E. Ramsay, PhD; Efstathios Papachristou, PhD; Richard