Thursday, January 18, 2018

Blasting dental plaque with microbubbles


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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.

Tuesday, January 16, 2018

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.

Thursday, January 4, 2018

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

Tuesday, December 19, 2017

Possible markers for earlier diagnosis of aggressive tongue cancer



Squamous cell carcinoma of the tongue, also known as oral tongue cancer, is an aggressive form of cancer that generally affects older people. Patients with the disease often find it difficult to eat, swallow food, or speak. Reasons for its generally poor prognosis include late detection, before pain usually starts and only when physical symptoms such as lesions are present, and a propensity for spreading to other sites in the body.

But in a potential harbinger of hope for arriving at an earlier diagnosis and treatment, in a new study published in Oncotarget, a team of researchers from Case Western Reserve University School of Medicine, Cleveland Clinic, and University Hospitals Cleveland Medical Center has found that bacterial diversity and richness, and fungal richness, are significantly reduced in tumor tissue compared to their matched non-tumor tissues.

This raises the prospect that certain bacteria and fungi, in sufficient amounts and in possibly interactive ways, may play a part in the development of oral tongue cancer. (Previous research has shown that bacteria can spur gastric and colorectal cancer and that bacterial/fungal interplay can contribute to or exacerbate Crohn's disease.)

"Our findings mean that it may be possible to perform precautionary testing in patients at high-risk for oral tongue cancer," said the study's co-senior author Mahmoud A. Ghannoum, PhD, professor in the Department of Dermatology at Case Western Reserve School of Medicine and University Hospitals Cleveland Medical Center. "If the patterns that we found are present in people who are not yet showing signs of lesions, we could begin treatment early, offering the possibility of better patient outcomes."

Oral tongue cancer, which arises in the anterior two-thirds [front] of the tongue, has been rapidly increasing and is now the second most common malignancy in the oral cavity. While human papillomavirus causes nearly ninety percent of base-of-tongue tumors [back], HPV is rarely found (only 2.3 percent) in oral tongue cancer. The causes of oral tongue cancer are unclear, but genetic mutations probably play a role, while smoking and chewing of tobacco, alcohol use, and poor dental hygiene are correlated with the development of this type of cancer.

"Poor oral hygiene has long been associated with oral cancers, suggesting that oral bacteriome (bacterial community) and mycobiome (fungal community) could play a role," said co-senior author Charis Eng, MD, PhD, professor and vice chairman of the Department of Genetics and Genome Sciences at Case Western Reserve School of Medicine and Hardis Chair of the Genomic Medicine Institute at the Cleveland Clinic.

While the bacteriome is increasingly recognized as playing an active role in health, the role of the mycobiome has been much less studied, and never before in the case of oral tongue cancer. In the new study, the researchers extracted tissue DNA from 39 paired tumor and adjacent normal tissues from patients with the cancer. Analyses showed that Firmicutes was the most abundant bacterial phylum, and was significantly increased in tumor compared to non-tumor tissue, 48 percent vs. 40 percent, respectively.

In total, the abundance of 22 bacterial and seven fungal genera [types] was significantly different between the tumor and adjacent normal tissue, including Streptococcus, which was significantly increased in the tumor group (34 percent vs. 22 percent in normal tissue.)

"Studies are starting to emerge demonstrating interactions between bacteria and fungi in the formation of disease," said Ghannoum. "Thus, additional research is needed aimed at understanding how these two communities influence or are influenced in disease settings such as oral tongue cancer."

Monday, December 4, 2017

New dental material resists plaque and kills microbes

                     


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 a new study, researchers from the University of Pennsylvania evaluated a new dental material tethered with an antimicrobial compound that can not only kill bacteria but can also resist biofilm growth. 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," said Geelsu Hwang, research assistant professor in Penn's School of Dental Medicine, "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. 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."
Hwang collaborated on the study, which was published in the journal ACS Applied Materials and Interfaces, with Penn Dental Medicine professor Hyun (Michel) Koo and Bernard Koltisko and Xiaoming Jin of Dentsply Sirona.
The newly developed material is comprised 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 said.
Hwang and colleagues 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.
Hwang, who has an engineering background, has welcomed the opportunity to apply his unique expertise to problems in the dental field. Looking ahead, he looks forward to further opportunities to develop and test innovative products to preserve and restore oral health.

Saturday, December 2, 2017

Jawbone loss predates rheumatoid arthritis

                     


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IMAGE: In the above x-ray image, the white dotted line indicate the normal jawbone level at a molar site in the lower jaw. The individual has periodontitis and has therefore lost... view more 
Credit: Pernilla Lundberg and Solbritt Rantapää-Dahlqvist
Jawbone loss caused by periodontitis predates the onset of rheumatoid arthritis. This according to research from Umeå University in Sweden presented in the journal Arthritis & Rheumatology. The research also shows a causal relationship between jawbone loss and elevated levels of the bone resorption inducing molecule RANKL in the blood.
Jawbone loss caused by inflammation is characteristic to both periodontitis - a disease leading to tooth loss - and rheumatoid arthritis. Despite differences in what causes the inflammation in periodontitis or rheumatoid arthritis, it has now been established that there is a correlation between the two.
"For example, it's known that individuals with rheumatoid arthritis to a great extent show symptoms of tooth loss than individuals with healthy joints. It's also been known that treatments aimed at periodontitis also ease symptoms from joints in individuals with rheumatoid arthritis. What's not been proven so far, however, is a causal relationship between the two," says Pernilla Lundberg, senior lecturer at the Department of Odontology at Umeå University, and one of the researchers behind the study.
In a collaboration, Pernilla Lundberg and Solbritt Rantapää-Dahlqvist, who is a researcher at the Department of Public Health and Clinical Medicine at Umeå University, have analysed the prevalence of jawbone loss in dental x-rays of individuals with rheumatoid arthritis. The X-rays were performed before arthritis symptoms had developed, and were compared with X-rays from matching controls. All participants in the study had on numerous occasions donated blood to the Medical Biobank Northern Sweden Health and Disease Study. Dental X-rays had been retrieved from the treating dentists.
The results, now presented in the journal Arthritis & Rheumatology, show for the first time that the individuals who later develop rheumatoid arthritis to a greater degree show signs of jawbone loss. Individuals with rheumatoid arthritis also to a greater extent develop jawbone loss over time. Among the individuals who later developed rheumatoid arthritis, the greatest degree of bone loss was detected in individuals who also showed elevated levels of the bone resorption inducing molecule RANKL in the blood.
"As far as we know, no one has previously been able to show that individuals who later develop rheumatoid arthritis have a higher degree of jawbone loss before showing any symptoms of arthritis," says Solbritt Rantapää-Dahlqvist.
"Our results indicate a causal relationship between periodontitis and rheumatoid arthritis. Nevertheless, further clinical studies and studies on basic mechanisms are needed in order to prove the existence of a causal relationship with certainty."