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

                     


IMAGE
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."

Monday, November 27, 2017

Immune deficiency explains rampant caries in some children

                    


Researchers at Umeå University in Sweden have made a novel discovery connecting genetic innate immunity deficiencies to rampant caries and increased risk of dental caries affecting about one in five children. The results could lead to a better way of identifying high-risk patients and treat their caries. The study has been published in the journal EBioMedicine.

In a five-year study, in which saliva and isolated bacterial strains from a large number of children was analyzed and the dental health monitored, the research group recently established that some high-risk children have a more virulent variant of the caries bacterium Streptococcus mutans. The same research group now shows that high-risk children also have genetic defects in innate and adaptive immunity, making them more vulnerable against oral bacteria and streptococci in general.

"Most people consider caries to be a lifestyle condition caused by bad eating- and oral hygiene routines that lead to acidic pH levels in the mouth, which in turn damage the enamel and promote the colonization of acid-producing bacteria such as S. mutans," says Nicklas Strömberg, professor and Head at the Department of Cariology at Umeå University and Västerbotten County Council, and first author of the article.

"Our results now show that this correlation is accurate for approximately four out of five individuals, who have a small-to-moderate risk of developing caries because their composition of salivary innate immunity proteins make them relatively resistant to caries. However, we have shown that so-called high-risk individuals, which are about one in five individuals, carry a genetically different composition of the same salivary innate immunity proteins, making them highly susceptible to caries independent of eating- or oral hygiene habits or S. mutans-infection."

One in five children in Sweden is considered a high-risk individual when it comes to the risk of developing dental caries. These high-risk individuals do not respond to traditional caries prevention or treatment, and bio markers cannot predict future risk of caries in the group. Chronic caries infection and missing teeth are also risk factors for systemic diseases such as stroke and cardiovascular diseases.

Innate and adaptive immunity deficiencies explain high-risk individuals for caries

A research group led by Nicklas Strömberg have in the current study followed 452 children (between ages 12 and 17) in Västerbotten over a five year period. After genetic analysis of their DNA, the children were divided into various risk groupings based on genetic variation in PRH1 and PRH2, encoding salivary acidic proline-rich proteins. At a five-year follow-up, the researchers could see how caries had developed in the various risk groupings.

The results showed that children with high susceptibility or risk for caries had defective proteins in their saliva. The defective salivary proteins in question were acidic and basic proline-rich proteins and the adhesive protein salivary agglutinin (or DMBT1). According to the researchers, the defective proteins probably fail to mediate the same innate and adaptive immunity responses that serve to protect individuals with small-to-moderate caries risk from the oral bacterial flora.

The researchers describe how allelic variation in PRH1 and PRH2, encoding acidic proline-rich proteins, separate children into different caries susceptibility or risk groupings. As expected, children with a low-to-moderate susceptibility or risk for caries along with a genetically intact set of proteins were found to develop caries from bad eating and oral hygiene routines and S. mutans-infection.

However, the children with high susceptibility develop caries independent of eating- or oral hygiene routines or S. mutans-infection but from the immune deficiency. Accordingly, when children were treated with dental braces the high risk children exclusively developed several times more caries after 5 years. The researchers believe this is due to plaque accumulation and impaired saliva flow as a result from the dental braces.

"This new knowledge about genetic susceptibility groupings could be used to improve individualized dental care. Children in the higher risk group could then be diagnosed before caries lesions and symptoms arise. In this way, prevention could be implemented at a young age when caries can be prevented more easily. High-risk children can presently be treated with intensified prevention and in the future we will hopefully be able to use immune-supplementation as a way to strengthen their oral immunity," explains Nicklas Strömberg.

Dental costs, including those pertaining to caries treatment, amount to 5 % of global health care-related costs. Caries is the most common cause for failure of fillings and prosthetic replacements. The ability to detect high-risk individuals early could yield large savings for society and individuals both in terms of suffering and costs.

Increased oral pathogens, decreased bacterial diversity predict precancerous stomach cancer lesions

                    


Elevated pathogen colonization and a lack of bacterial diversity in the mouth were identified in people with precancerous lesions that could precede stomach cancer, finds a new study led by New York University College of Dentistry (NYU Dentistry) and New York University School of Medicine.

The findings, published in the November issue of the Journal of Periodontology, provide new evidence that the increase in pathogens associated with periodontal disease - a chronic, destructive disease in the gums and oral cavity - could contribute to the development of precancerous lesions of stomach cancer.

"Our study reinforces earlier findings that poor oral health is associated with an increased risk of precancerous lesions of stomach cancer," said Yihong Li, DDS, MPH, DrPH, professor of basic science and craniofacial biology at NYU Dentistry and the study's corresponding author.

The American Cancer Society estimated that 26,370 new cases of stomach or gastric cancer would be diagnosed in 2016, resulting in 10,703 deaths. Accumulating evidence suggests that chronic inflammation caused by oral bacterial infections may contribute to the development and progression of various types of cancer, including stomach cancer.

Although some risk factors - such as H. pylori colonization, cigarette smoking, and eating salt and preserved foods - have previously been confirmed to contribute to the development of stomach cancer, many new cases unrelated to these risk factors are diagnosed each year. Scientists have hypothesized that a group of pathogens may be responsible for causing periodontal disease and the resulting chronic systemic inflammation that may contribute to the development of gastric cancer.

This study assesses the association between periodontal pathogen colonization and the potential risk of developing precancerous lesions - including chronic atrophic gastritis, intestinal metaplasia, and dysplasia - that may predict stomach cancer.

The researchers studied 105 individuals scheduled to receive an upper endoscopy. After the endoscopic procedure and histopathologic evaluation, 35 people were diagnosed with precancerous lesions of gastric cancer and another 70 people of the same ages without precancerous lesions were included in the study as a control group.

The researchers performed full-mouth examinations to assess participants' periodontal conditions. Saliva and dental plaque samples were collected to evaluate colonization by several of pathogens - P. gingivalis, T. denticola, T. forsythia, and A. actinomycetemcomitans - and to characterize oral microbial diversity.

Compared with the control group, patients with precancerous lesions experienced higher prevalence of bleeding when probed (31.5 percent versus 22.4 percent), higher levels of two pathogens (T. denticola and A. actinomycetemcomitans), and less bacterial diversity in their saliva.

A further analysis, which took into account sociodemographic factors, oral health behaviors, and periodontal assessments, revealed additional predictors of precancerous lesions: elevated colonization of three pathogens (T. forsythia, T. denticola, and A. actinomycetemcomitans), decreased bacterial diversity in dental plaque, and not flossing regularly.

The researchers concluded that the colonization of periodontal pathogens and the alternated bacterial diversity in the oral cavity are important factors that, when at higher or lower levels respectively, may contribute to an increased risk of developing precancerous gastric lesions.

"Based on our findings, treatment for chronic periodontal disease and control of periodontal pathogen infections should be included in future strategies for preventing stomach cancer," said Dr. Li.

Friday, November 17, 2017

Methodologies in orthodontic pain management: A review

                     


Patients experience pain and discomfort during active orthodontic treatment with fixed appliances. It can vary from person to person and is influenced by certain factors such as age, gender, previous pain experiences, stress or anxiety, and type of appliance.

The objective of this literature review was to discuss conventional versus recently introduced treatment modalities used in pain management for orthodontic patients.

According to the reviewed articles, both pharmacological and non-pharmacological methods were introduced in orthodontic pain management. However, orthodontists must use their best professional judgment to assess each case individually and select an appropriate treatment modality based on pain threshold level of an individual.

Research Key Points
  • Effective orthodontist-patient communication and targeted nutritional guidance may help in preventing pain and discomfort experienced by the patients to some extent.
  • However, based on the available literature, analgesics remained the effective and routine methodology of pain management.
  • Some clinicians supported that NSAIDs such as Ibuprofen had no impact on tooth movements as they were administered in lower doses and for a shorter duration. Hence, Ibuprofen was considered a safe and effective drug compared to other NSAIDs. On the contrary, other authors declared a delay in orthodontic tooth movements as a result of NSAID intake.
  • Another investigation supported that paracetamol (acetaminophen) was considered the safest NSAID that had no influence on the range of tooth movements as well as root resorption. However, much of what has been published on this subject is still controversial.
  • Moreover, while prescribing analgesics, orthodontists must be aware of the pharmacological action as well as the pros and cons related to each drug.
  • Nevertheless, pain management is a complex phenomenon. Therefore, further investigations combining different methods of orthodontic pain control with appropriate study designs and large sample sizes are required to improve the quality of evidence.

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For more information about the article, please visit https://benthamopen.com/ABSTRACT/TODENTJ-11-492
  • Reference: Hussain AS, et al. Methodologies in Orthodontic Pain Management: A Review. The Open Dentistry Journal, 2017, Vol 11, DOI: 10.2174/1874210601711010492

Tooth cavities can be fought 'naturally'


A new discovery may one day lead to natural anti­cavity products, researchers report.

The scientists from West China School of Stomatology and Academic Centre for Dentistry Amsterdam have figured out the main active ingredient of Galla Chinensis, a natural herb, and further improved its anti-caries efficacy. The finding is published in The Open Dentistry Journal.

To maintain a healthy mouth, the oral environment must be relatively neutral. When the environment in the mouth becomes more acidic, dental cavities or other disorders may develop. Galla Chinensis was revealed to inhibit the acid production of caries-associated bacteria as well as make teeth more resistant to acidic attack.

The research team of West China School of Stomatology has tested hundreds of Chinese herbs and identified that Galla Chinensis has a strong potential to prevent dental caries due to its antibacterial capacity and tooth mineralization benefit. Galla Chinensis also possesses substantial antiviral, anticancer, hepatoprotective, antidiarrheal and antioxidant activities. However, the main active ingredient of Galla Chinensis is unknown, which restricts the application in dentistry.

In the present study, several Galla Chinensis extracts with different main ingredients were obtained and determined by liquid chromatography-mass spectrometry (LC-MS) analysis. The antibacterial capacity was determined using the polymicrobial biofilms model, which can generate reproducible plaque-like biofilms that occur in vivo. The effect of inhibiting tooth demineralization was tested using an in vitro pH-cycling regime, which mimicked the periodic pH change in mouth.

"Medium molecular weight gallotannins are the most active constituent in terms of caries prevention" concluded Xuelian Huang, PhD, DDS, the lead author.

In dental caries, significant reductions in caries prevalence and incidence have been made by the introduction of fluoride. It is not a total cure, however, and there is still a need to seek products complementary to fluoride. With these new findings, the research team is working with the industry to develop new oral care products.
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For more information about the article, please visit https://benthamopen.com/ABSTRACT/TODENTJ-11-447
Reference: Zhou X, et al. Comparison of Composition and Anticaries Effect of Galla Chinensis Extracts with Different Isolation Methods. The Open Dentistry Journal, 2017, Vol 11, DOI: 10.2174/1874210601711010447

Naturally occurring molecule may help prevent and treat atherosclerosis and gum disease

                    

Resolvin E1, a molecule produced naturally in the body from an omega -3 fish oil, topically applied on gum tissues not only prevents and treats gum disease as previously shown (Hasturk et al 2006 and 2007), but also decreases the likelihood for advanced arterial atherosclerotic plaques to rupture and form a dangerous thrombus or blood clot.

The findings, which appear in the journal Current Atherosclerosis Reports, could lead to effective preventive and therapeutic treatments in people with heart disease and/or gum disease without unwanted side effects.

Inflammation is a key pathology of atherosclerosis and may be a major driving force for heart attacks and stroke. There is increasing evidence from numerous research groups that chronic inflammatory diseases including, diabetes, heart disease, rheumatoid arthritis, colitis, pulmonary and kidney diseases, cancer and Alzheimer's disease can benefit by the use of the pro-resolving lipid mediators, resolvins and lipoxins.

To test the effectiveness of lipid mediators on advanced atherosclerosis, researchers from Boston University School of Medicine (BUSM) and The Forsyth Institute used two groups of an experimental model that possessed highly inflamed advanced atherosclerosis.

The first group was treated with a solution applied on gum tissues that contained Resolvin E1 while the second group was treated with salt water as a control.

The group treated with the inflammation-lowering lipid mediator (Resolvin E1) had minimal atherosclerosis and reduced plaque rupture in their aortic artery, while atherosclerosis advanced to more severe form of the disease in the control (salt water) group.

"Current therapies for advanced atherosclerosis are inadequate and often carry high risks, and the Resolvin E1 therapy could provide a very effective and safe therapy that can be taken daily, which would also serve as a preventive approach for plaque inflammation and acute clinical events of heart attack and stroke," explained corresponding author James A. Hamilton, PhD, professor of physiology and biophysics and research professor of medicine at BUSM.

The researchers believe these findings support a paradigm shift in the treatment of both localized and systematic inflammatory conditions that are increasingly prevalent in type 2 diabetes and obesity and may be applicable to other chronic inflammatory diseases.