Researchers have found that isolating a particular gene within the oral microbiome can reveal a huge amount of useful diagnostic information about a person’s health

Most people don’t think of dental plaque when they think about clinical laboratories. For the vast majority of people, the only diseases that dental plaque bring to mind are those of the mouth:

gingivitis;
periodontitis; and,
dental caries.

Samples that are sent to medical labs and pathology laboratories are more often blood or tissue. However, that could be changing, thanks in part to the work being done at the Oral Microbiome and Metagenomics Research Lab (OMMR) at the University of Toronto.

Plaque and the Oral Microbiome as Biomarkers for Medical Lab Tests

The OMMR researchers discovered that isolating a particular gene within the oral microbiome can reveal a huge amount of information about a person’s health. The gene is 16S ribosomal RNA (16S rRNA). It is a bit like a fingerprint in that it is both present and unique in all bacteria, including the bacteria in dental plaque. The 16S rRNA serves as a reference point in a plaque sample, and helps researchers identify all of the bacteria in a given sample.

By comparing dental plaque samples from the mouths of healthy people to those from people with specific diseases, researchers can begin to map biomarkers that could provide information about health risks.

Why a Plaque Bank Could Contribute to New Clinical Lab Assays

An article published in Medical Design Technology (MDT) describes the work as “creating a comprehensive catalogue of health through the kind and number of bacteria in the human oral microbiome.” More simply put, it could be described as a plaque bank.

In the MDT article, David Lam, MD, DDS, PhD, of the University of Toronto says, “We’re providing a bacterial surveillance service to patients.” He goes on to explain that the team at OMMR wants to eventually “monitor disease progression and response to therapies” through dental plaque analysis.

David Lam, MD, DDS, PhD is Assistant Professor, Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Toronto. (Photo copyright: LinkedIn.)

David Lam, MD, DDS, PhD is Assistant Professor, Oral and Maxillofacial Surgery, Faculty of Dentistry, University of Toronto. (Photo copyright: LinkedIn.)

One reason for the research into using dental plaque as a method for collecting samples for analysis, and possibly diagnosis of various diseases, is that it is such a dynamic microbial community. Sometimes referred to as biofilm, an article on the National Institute of Dental and Craniofacial Research website describes dental plaque as “a dynamic, polymicrobial community, that, like lichens growing along a craggy coast, colonizes various and sundry pits, fissures, and other oral surfaces.”

Previous Work on Disease Identification Using the Oral Microbiome

The work at OMMR is innovative because it focuses on diseases that are not generally associated with dental plaque. Before the leap to other types of diagnostics could be taken, other scientists studied the oral microbiome in relation to periodontitis. In a landmark paper published on the National Center for Biotechnology Information (NSBI) website, Jorge Frias-Lopez, PhD, a scientist/researcher at the Forsyth Institute, and several colleagues reported “the in situ genome-wide transcriptome of the subgingival microbiome in six periodontally healthy individuals and seven individuals with periodontitis.” Such studies led by researchers providing the composition of the oral microbiome have, in turn, led to the knowledge that dental plaque holds information about the rest of the body’s function.

Jorge Frias-Lopez, PhD, is Associate Member of the Staff and Vice Chair, Department of Microbiology at the Forsyth Institute, Cambridge, Massachusetts, and Lecturer in Oral Medicine, Infection, and Immunity at Harvard School of Dental Medicine. (Photo copyright: Forsyth Institute.)

Jorge Frias-Lopez, PhD, is Associate Member of the Staff and Vice Chair, Department of Microbiology at the Forsyth Institute, Cambridge, Massachusetts, and Lecturer in Oral Medicine, Infection, and Immunity at Harvard School of Dental Medicine. (Photo copyright: Forsyth Institute.)

The Problem with Saliva as a Specimen for Diagnostic Purposes

Saliva has been used for diagnostic purposes for quite some time. In a 2011 article published on the NCBI website, Daniel Malamud, PhD, wrote “Salivary diagnostics is a dynamic and emerging field utilizing nanotechnology and molecular diagnostics to aid in the diagnosis of oral and system diseases.” However, the problem with using saliva is that “bacterial numbers in saliva can ebb and flow over the course of a day, fluctuating based on everything from what you ate for breakfast to your sleep cycles,” according to the MDT article. The microbial communities in dental plaque, on the other hand, remain stable, making it possibly a more reliable source of information.

Daniel Malamud, PhD, is Professor of Basic Science, NYU College of Dentistry; Professor of Medicine (Infectious Diseases), NYU School of Medicine; and, Director of HIV/AIDS Research Program (HARP), NYU College of Dentistry. (Picture copyright: NYU College of Dentistry.)

Daniel Malamud, PhD, is Professor of Basic Science, NYU College of Dentistry; Professor of Medicine (Infectious Diseases), NYU School of Medicine; and, Director of HIV/AIDS Research Program (HARP), NYU College of Dentistry. (Picture copyright: NYU College of Dentistry.)

Conflicting Results from this New Field of Diagnostics

This branch of study is new, and, so far, there are some conflicting results. A good example is the research regarding helicobacter pylori in dental plaque and gastric infection.

A study published on the NCBI website conducted in 2006 concluded, “There is not any significant association between the helicobacter pylori of the dental plaque and the stomach. Also the dental plaque cannot be used as a primary diagnostic aid for gastric infection.” However, a more recent study published in 2014 found, “There is a close relation between H. pylori infection in the oral cavity and the stomach. The mouth is the first extra-gastric reservoir.”

Future Research Plans

One of the ways researchers at OMMR plan to pursue future studies is “to create an artificial mouth that mimics the physical and physiological conditions of the human oral cavity to help them carry out their biomarker identification process.” Future research will also investigate so-called “plaque transplantation” therapies, such as placing select plaque samples into the mouths of patients who have undergone radiation therapy, which sometimes causes rapid tooth decay. The procedure could “stabilize the bacterial content of the mouth.”

Harvesting dental plaque is non-invasive, and a complete analysis can be completed in just a few hours. As this line of research continues, and the scientists at OMMR compile the plaque bank, biofilm samples could become powerful diagnostic tools. If this were to happen and further studies validate the use of plaque as a biomarker, then the day might come when clinical laboratories will provide lab testing services to dentists.

—Dava Stewart

Related Information:

Putting Your Money Where Your Mouth Is? Dentistry’s New Plaque Bank Collects Evidence On the Mouth as the New Frontier for Medicine

Diagnosing Disease Through Dental Plaque 

The Oral Microbiome: From Bad Bugs to Bad Biofilm Behaviors 

Community-Wide Transcriptome of the Oral Microbiome in Subjects With and Without Periodontitis 

Saliva as a Diagnostic Fluid

Helicobacter Pylori in the Dental Plaque: Is It of Diagnostic Value for Gastric Infection? 

Helicobacter Pylori and Oral Pathology: Relationship with the Gastric Infection 

Cornell Researchers Identify Gut Microbes that May Help Some People Remain Thin; Findings Could Result in Clinical Laboratory Tests to Analyze the Microbiomes of Individuals

Effort to Map Human Microbiome Will Generate Useful New Clinical Lab Tests for Pathologists

Get the Poop on Organisms Living in Your Gut with a New Consumer Laboratory Test Offered by American Gut and uBiome

Expanding Knowledge about the Human Microbiome Will Lead to New Clinical Pathology Laboratory Tests