Brochure | Dental and Oral Health

Oral Bacteria Diversity Linked to Depression Symptoms

2025-06-12 - 2025-06

Summary: A new study reveals that lower diversity of microbes in the mouth is associated with greater symptoms of depression. Researchers analyzed data from over 15,000 U.S. adults, comparing their mental health surveys with saliva samples to assess microbial diversity.
The findings show that people with less diverse oral microbiomes were more likely to experience depression, even after accounting for factors like smoking and dental care. While the direction of this link is still unclear, the study suggests the oral microbiome may one day be used to help diagnose or treat mood disorders.
Key Facts:
Microbial Diversity Matters: People with lower oral microbiome diversity showed more depressive symptoms.
Lifestyle Factors Influence Microbes: Smoking, drinking, and dental care affected the depression-microbiome link.
Diagnostic Potential: With further research, oral bacteria could serve as biomarkers for depression.
A rich and varied mix of microbes in the mouth, particularly bacteria, is not only important for our oral health, but may hold clues for other conditions.
A new study led by researchers at NYU Rory Meyers College of Nursing finds that a lower diversity of microbes in the mouth is associated with depression.
The mouth is home to between 500 billion and 1 trillion bacteria-the second-largest community of microorganisms in our bodies, after the gut.
A growing number of studies point to the connection between the oral microbiome and our overall health, from diabetes to dementia, a relationship thought to be driven by inflammation and disruptions to the immune system.
A recent study in mice found a potential link between depression and the diversity of bacteria in the gut, but less is known about the connection between the oral microbiome and depression.
"Having a better understanding of the relationship between the oral microbiome and depression could not only help us learn about the mechanisms underlying depression, but could contribute to the development of new biomarkers or treatments for mood disorders," said Bei Wu, vice dean for research at NYU Rory Meyers College of Nursing and the senior author of the study, published in the journal BMC Oral Health.
To explore the connection between the oral microbiome and depression, the researchers examined survey and biological data from the National Health and Nutrition Examination Survey (NHANES), conducted by the Centers for Disease Control and Prevention.
Using data from more than 15,000 US adults ages 18 and older collected between 2009 and 2012, the researchers compared questionnaires measuring symptoms of depression with saliva samples. Gene sequencing was used to identify the microbes in the saliva and measure the diversity of the oral microbiome.
The researchers found that people with less diversity in their oral microbiomes were more likely to have symptoms of depression. Additional analyses showed that smoking, drinking, and dental care-all of which can change the makeup of bacteria in the mouth-influenced the relationship between the oral microbiome and depression.
These findings suggest that, with more research, the oral microbiome could potentially be used to diagnose or treat depression. However, based on this study, it's not clear whether the diversity of microbes in the mouth influences depression or if depression leads to changes in the oral microbiome-or if there's a bidirectional relationship between the two.
"It's possible that the oral microbiome influences depressive symptoms through inflammation or changes to the immune system. Conversely, depression can drive changes including dietary intake, poor oral hygiene, increased smoking and drinking, or the use of medications-all of which have the potential to alter the oral microbiome," said Wu.
"We need more research to understand the direction and underlying pathways of this relationship."
"This work is part of a broader effort to understand how the oral microbiome influences not only mental health, but also cognitive decline and the onset of dementia," she added.

National fluoride ban would substantially increase children's tooth decay and dental costs, modeling study finds

2025-05-30 - 2025-05

Fluoride has been added to public water systems in the United States since 1945 to strengthen tooth enamel and fight off bacteria, ultimately reducing tooth decay. Mass General Brigham researchers developed a model to estimate dental health outcomes for children if the United States were to ban fluoridation of public water. The new study, published in JAMA Health Forum, found that banning fluoride would substantially increase dental decay and costs particularly for publicly insured and uninsured children.
"Fluoride replaces weaker ions within tooth enamel, making it stronger and less susceptible to tooth decay caused by bacteria," said senior author Lisa Simon MD, DMD, Division of General Internal Medicine at Brigham and Women's Hospital.
"There's strong evidence from other countries and cities, such as Calgary in Canada, showing that when fluoride is eliminated, dental disease increases. Our study offers a window into what would happen in the United States if water fluoridation ceased."
Simon and the research team focused on children for the study, because fluoride strengthens teeth during development, and more robust data links fluoridated water to oral health in this age group.
The study used detailed oral health and water fluoridation data collected from 8,484 children (ages 0-19, 49% girls) in the nationally representative National Health and Nutrition Examination Survey (NHANES). Using this dataset, the researchers developed a microsimulation model to see how banning fluoride from drinking water would impact oral health, quality of life and dental care costs.
The researchers simulated two scenarios over 5- and 10-year periods, which align with policy planning horizons. First, maintaining current fluoride levels, and second, eliminating the addition of fluoride to public water.
"Using a simulation model to track the progression of diseases in current populations, we estimated the impact of removing fluoride on the risk of tooth decay and the related dental care costs, including treatment for decay and complications from delayed treatment.
"We ran the simulation 1,000 times to see how different factors could affect the results. This approach helps ensure that our predictions are more reliable and reflective of real-world variability," said first author Sung Eun Choi, Ph.D., assistant professor of Oral Health Policy & Epidemiology at Harvard School of Dental Medicine.
The researchers found that eliminating fluoride increased the total number of decayed teeth by 7.5 percentage points, or 25.4 million more teeth with tooth decay over five years (equivalent to a tooth for one out of every three American children). The number of fluorosis cases-a discoloring of tooth enamel due to excessive fluoride intake-decreased by 0.2 million. They also estimated a cost of $9.8 billion in additional dental care costs over five years, which rose to $19.4 billion after 10 years.
"Most of the increased cost could be attributed to publicly insured children, meaning it would be a direct public health cost," said Simon.
The study did not model cognitive effects from fluoride exposure as current levels of fluoride in public water are not associated with worse neurobehavioral outcomes. The researchers note that their model demonstrates meaningful, ongoing benefit from fluoride at safe levels currently recommended by the Environmental Protection Agency, the National Toxicity Program, and the Centers for Disease Control and Prevention.
"We know fluoride works. We're able to show just how much it works for most communities and how much people stand to lose if we get rid of it," said Simon.

Minamata Convention: Study proposes 'leapfrogging' implementation of children's amendment

2025-05-27 - 2025-05

A recently published article has proposed a unique strategy on oral health policy as a cost-effective strategy for African countries to achieve mercury-free dentistry.
Tagged "leapfrogging", the strategy, according to the authors, could also be adopted by developed economies with underserved communities as well as developed economies who desire to save costs.
The unique, cost-effective strategy is to "leapfrog" the implementation of the children's amendment to the Minamata Convention on Mercury (COP 4.2) in Africa and other developing economies.
According to the paper, titled "Update of Oral Health Policy to Implement the Children's Amendment to the Minamata Convention on Mercury (COP 4.2)", the cornerstones of the strategy include update of dental training institutions curricula, review of health insurance policies, integration of the principles of minimum intervention dentistry (MID) into oral health policies with an integration-prevention-promotion-partnerships ('II-PPP') framework with the WHO Basic Package for Oral Care.
"We hope this approach will enhance the speedy implementation of the children's amendment particularly in Africa and other developing economies with poor infrastructure for managing waste," submitted Professor Godwin Arotiba, the lead author.
The article was published in the Journal of Oral Health & Dental Science.
The founder of Dentists for a Mercury-Free Africa and the former Dean of Lagos University Teaching Hospital (LUTH), Professor Arotiba engaged with several Nigerian professors from his and three other top-notch universities, plus NGO leaders in Nigeria and Cameroun, to produce the landmark paper.
"We have been at this for so long now since 2014 to date. We need to leapfrog to mercury free 21st century dentistry by 2030 in Africa, Other developing economies and developed economies with underserved communities, plus developed economies who desire to save costs as well," said Aritoba.
The paper concluded: "'Leapfrogging' to mercury free 21st century dentistry is a feasible, desirable and achievable strategy to adopt for Africa and other developing economies with poor infrastructure for managing wastes.
"It can also be adopted by developed economies with underserved communities as well as developed economies who desire to save costs. The top priorities should include update of dental training institution's curricula; retraining of general dental practitioners through workshops, conferences, and webinars; update of health insurance policy to favour mercury free restoratives and update of oral health policies with the 'II-PPP-BPOC' framework.
"Poverty should not be an excuse to continue the use of dental amalgam (45-55% mercury) in under-served communities and further compromise their well-being. This is a very important consideration in Sub-Saharan Africa where UNEP and WHO have reported a higher percentage (35%) of diseases traced to environmental pollution compared to 25% world-wide."
The Minamata Convention on Mercury is an international treaty designed to protect human health and the environment from anthropogenic emissions and releases of mercury and mercury compounds. It contains, in support of this objective, provisions that relate to the entire life cycle of mercury, including controls and reductions across a range of products, processes and industries where mercury is used, released or emitted.
The Children's Amendment to protect children from the harm of mercury containing fillings entered into force on September 28, 2023, and became mandatory for Parties to the Minamata Convention.
Henceforth, all the 152 nations who are Parties to the treaty must take affirmative steps - ranging from recommendations to complete abolition - to end amalgam use for children, pregnant women, and breastfeeding mothers.

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Oral Bacteria Diversity Linked to Depression Symptoms

National fluoride ban would substantially increase children's tooth decay and dental costs, modeling study finds

Minamata Convention: Study proposes 'leapfrogging' implementation of children's amendment