Inflammation in mouth, joints in rheumatoid arthritis

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At the 93rd General Session and Exhibition of the International Association for Dental Research, researcher Sheila Arvikar, Massachusetts General Hospital, Boston, USA, will present a study titled "Inflammation in the Mouth and Joints in Rheumatoid Arthritis." The IADR General Session is being held in conjunction with the 44th Annual Meeting of the American Association for Dental Research and the 39th Annual Meeting of the Canadian Association for Dental Research.

Periodontitis shares pathogenic mechanisms with rheumatoid arthritis (RA) and may trigger its onset. In this study, researchers performed joint and dental examinations, determined Porphyromonas gingivalis (P. gingivalis) antibodies, and examined inflammatory microenvironments in early and chronic RA patients.

Twenty-three RA patients, (15 new-onset disease, eight chronic) and 20 age/gender-matched healthy subjects (HS) without periodontitis/RA were enrolled in this study. Serum P. gingivalis IgG antibodies were measured by ELISA. Twenty inflammatory mediators were measured in serum, saliva, gingival crevicular fluid (GCF), and joint fluid by Luminex.

The 23 patients (87% female) received routine dental care, except for one; none currently smoked. Of the 23 RA patients, 10 had gingivitis and nine had periodontitis. RA patients exhibited increased pocket depth, clinical attachment loss, bleeding on probing and GCF volume compared with HS. Six of 23 patients had P. gingivalis antibodies, and all six had periodontitis.
RA patients showed a marked inflammatory profile in all microenvironments, including oral, despite routine dental care. P. gingivalis antibodies can be considered as biomarkers for rheumatologists in identifying those who may benefit from periodontal treatment.

Graphene: A new tool for fighting cavities and gum disease?

Dental diseases, which are caused by the overgrowth of certain bacteria in the mouth, are among the most common health problems in the world. Now scientists have discovered that a material called graphene oxide is effective at eliminating these bacteria, some of which have developed antibiotic resistance. They report the findings in the journal ACS Applied Materials & Interfaces.

Zisheng Tang and colleagues point out that dentists often prescribe traditional antibiotics to get rid of bacteria that cause tooth decay or gum disease. But with the rise in antibiotic resistance, new approaches are needed to address these problems, which can lead to tooth loss. Previous studies have demonstrated that graphene oxide -- carbon nanosheets studded with oxygen groups -- is a promising material in biomedical applications. It can inhibit the growth of some bacterial strains with minimal harm to mammalian cells. Tang's team wanted to see if the nanosheets would also stop the specific bacteria that cause dental diseases.

In the lab, the researchers tested the material against three different species of bacteria that are linked to tooth decay and gum disease. By destroying the bacterial cell walls and membranes, graphene oxide effectively slowed the growth of the pathogens. The researchers conclude that the nanosheets could have potential uses in dental care.

Periodontal disease linked to increased risk of kidney disease

 In a study of blacks with normal kidney function, those with severe periodontal disease developed chronic kidney disease (CKD) at 4 times the rate of those without severe periodontal disease. The study that will be presented at ASN Kidney Week 2014 November 11¬-16 at the Pennsylvania Convention Center in Philadelphia, PA.

Periodontal disease is a chronic bacterial infection of the oral cavity, and it disproportionately affects African Americans. It's also been implicated as a potential risk factor for CKD. To investigate this potential link, researchers led by Vanessa Grubbs, MD (University of California, San Francisco) analyzed 699 African American adults who underwent complete dental examinations.

During an average follow-up of 4.8 years, there were 21 (3.0%) new CKD cases. Participants with severe periodontal disease had a 4.2-fold greater incidence of CKD after adjusting for various factors (age, sex, diabetes, hypertension, smoking, and income) compared with those without severe periodontal disease.

"Because periodontal disease is common and can be prevented and treated, targeting it may be an important path towards reducing existing racial and ethnic disparities in chronic and end-stage kidney disease," said Dr. Grubbs.

Salivary mucins play active role to fight cavities

		IMAGE: The viscoelastic properties of mucus and saliva are attributed to mucins, large glycoproteins that play a key role in host defense and maintaining a healthy microbiome. Human salivary mucins protect... Click here for more information.

Salivary mucins, key components of mucus, actively protect the teeth from the cariogenic bacterium, Streptococcus mutans, according to research published ahead of print in Applied and Environmental Microbiology. The research suggests that bolstering native defenses might be a better way to fight dental caries than relying on exogenous materials, such as sealants and fluoride treatment, says first author Erica Shapiro Frenkel, of Harvard University, Cambridge, MA.

S. mutans attaches to teeth using sticky polymers that it produces, eventually forming a biofilm, a protected surface-associated bacterial community that is encased in secreted materials, says Frenkel. As S. mutans grows in the biofilm, it produces organic acids as metabolic byproducts that dissolve tooth enamel, which is the direct cause of cavities. "We focused on the effect of the salivary mucin, MUC5B on S. mutansattachment and biofilm formation because these are two key steps necessary for cavities to form," says Frenkel.

		IMAGE: This is two overlayed fluorescent microscopy images ofStreptococcus mutans, the primary bacteria responsible for dental cavities. When S. mutans forms biofilms on the tooth surface, it produces organic acids... Click here for more information.

"We found that salivary mucins don't alterS. mutans' growth or lead to bacterial killing over 24 hours," says Frenkel. "Instead, they limit biofilm formation by keeping S. mutans suspended in the liquid medium. This is particularly significant forS. mutans because it only causes cavities when it is attached, or in a biofilm on the tooth's surface." She adds that the oral microbiome is better preserved when naturally occurring species aren't killed. "The ideal situation is to simply attenuate bacterial virulence," she says.

The study grew out of previous work in the investigators' laboratory showing that other types of mucins, such as porcine gastric mucins, had protective effects against common lung pathogens, says Frenkel. With this in mind, they suspected that salivary mucins would play a protective role, but they were not sure what that would be.

		IMAGE: This is a fluorescent microscopy image of a Streptococcus mutans biofilm. Click here for more information.

"Defects in mucin production have been linked to common diseases such as asthma, cystic fibrosis, and ulcerative colitis," says Frenkel. "There is increasing evidence that mucins aren't just part of the mucus for structure or physical protection, but that they play an active role in protecting the host from pathogens and maintaining a healthy microbial environment. We wanted to apply these emerging ideas to a disease model that is a widespread, global public health problem--cavities. We chose to study the interaction of MUC5B with Streptococcus mutans because it is the primary cavity-causing bacteria in the oral cavity."

The research makes a fundamental contribution to scientific understanding of host-microbe interactions, says principal investigator Katharina Ribbeck, of the Massachusetts Institute of Technology, Cambridge MA. "It is generating a paradigm shift from the textbook view of mucus as a simple catchall filter for particles, towards the understanding that mucus is a sophisticated bioactive material with powerful abilities to manipulate microbial behavior."