Study: Obesity raises the risk of gum disease by inflating growth of bone-destroying cells

Findings may improve understanding of chronic inflammatory, bone-related diseases that develop alongside obesity, such as gum disease, arthritis and osteoporosis

Peer-Reviewed Publication

UNIVERSITY AT BUFFALO

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IMAGE: THE GRAPHIC DEMONSTRATES HOW MDSC EXPANSION DURING OBESITY TO BECOME BONE DESTROYING OSTEOCLASTS DURING GUM DISEASE IS TIED TO INCREASED BONE LOSS AROUND TEETH. view more 

CREDIT: PHOTO: KEITH KIRKWOOD.

BUFFALO, N.Y. – Chronic inflammation caused by obesity may trigger the development of cells that break down bone tissue, including the bone that holds teeth in place, according to new University at Buffalo research that sought to improve understanding of the connection between obesity and gum disease.

The study, completed in an animal model and published in October in the Journal of Dental Research, found that excessive inflammation resulting from obesity raises the number of myeloid-derived suppressor cells (MDSC), a group of immune cells that increase during illness to regulate immune function. MDSCs, which originate in the bone marrow, develop into a range of different cell types, including osteoclasts (a cell that breaks down bone tissue). 

Bone loss is a major symptom of gum disease and may ultimately lead to tooth loss. Also known as periodontal disease, gum disease affects more than 47% of adults 30 years and older, according to the Centers for Disease Control and Prevention.

“Although there is a clear relationship between the degree of obesity and periodontal disease, the mechanisms that underpin the links between these conditions were not completely understood,” says Keith Kirkwood, DDS, PhD, professor of oral biology in the UB School of Dental Medicine.

“This research promotes the concept that MDSC expansion during obesity to become osteoclasts during periodontitis is tied to increased alveolar bone destruction. Taken together, this data supports the view that obesity raises the risk of periodontal bone loss,” says Kyuhwan Kwack, PhD, postdoctoral associate in the UB Department of Oral Biology. 

The study examined two groups of mice fed vastly different diets over the course of 16 weeks: one group a low-fat diet that derived 10% of energy from fat, the other group a high-fat diet that drew 45% of energy from fat.

The investigation found that the high-fat diet group experienced obesity, more inflammation and a greater increase of MDSCs in the bone marrow and spleen compared to the low-fat diet group. The high-fat diet group also developed a significantly larger number of osteoclasts and lost more alveolar bone (the bone that holds teeth in place).

Also, the expression of 27 genes tied to osteoclast formation were significantly elevated in the group fed a high-fat diet. 

The findings may shed more light on the mechanisms behind other chronic inflammatory, bone-related diseases that develop concurrently with obesity, such as arthritis and osteoporosis, says Kirkwood.

Additional investigators include Lixia Zhang, PhD, research scientist in the UB Department of Oral Biology; Jiho Sohn, doctoral candidate in the Jacobs School of Medicine and Biomedical Sciences at UB; Victoria Maglaras, student in the UB School of Dental Medicine; and Ramkumar Thiyagarajan, research scientist in the Jacobs School.

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JOURNAL

Journal of Dental Research

DOI

10.1177/00220345211040729 

Local exhaust ventilation to control dental aerosols and droplets

Dental procedures produce aerosols which contain oral microbes, creating potential for infectious disease transmission. This study, “Local Exhaust Ventilation to Control Dental Aerosols and Droplets” published in the Journal of Dental Research (JDR), investigated the effect of a Local Exhaust Ventilation (LEV) device on aerosols and droplets produced during dental procedures. These devices are designed to be placed over the patient’s mouth to capture aerosols and droplets at the source. 

Researchers at Newcastle University, England, conducted experiments on dental mannequins. Ten-minute crown preparations were performed with an air-turbine handpiece in a large open plan clinic, and full mouth ultrasonic scaling was performed for ten minutes in a single dental surgery. Fluorescein was added to instrument irrigation reservoirs as a tracer. In both settings, Optical Particle Counters (OPCs) were used to measure aerosol particles between 0.3 – 10.0 μm and liquid cyclone air samplers were used to capture aerosolised fluorescein tracer. An LEV device with High Efficiency Particulate Air (HEPA) filtration and a flow rate of 5,000 L/min was tested during the experiments. 

 

The results show that using LEV reduced the dispersion of aerosols from the air turbine handpiece by 90% within 0.5 m, and this was 99% for the ultrasonic scaler. The settling of larger droplets was also measured for the air-turbine, and this was reduced by 95% within 0.5 m when LEV was used.

 

"This study shows that the effect of LEV was substantially greater than suction alone for the air-turbine and was similar to the effect of suction for the ultrasonic scaler,” said IADR President Eric Reynolds, The University of Melbourne, Australia. “While no mitigation measure alone will completely eliminate risk, LEV appears to be a useful approach, which in addition to other measures, substantially reduces dispersion of aerosols, and therefore risk of exposure to pathogens."

Baby teeth may one day help identify kids at risk for mental disorders later in life

Peer-Reviewed Publication

The thickness of growth marks in primary (or “baby”) teeth may help identify children at risk for depression and other mental health disorders later in life, according to a groundbreaking investigation led by researchers at Massachusetts General Hospital (MGH) and published in JAMA Network Open. The results of this study could one day lead to the development of a much-needed tool for identifying children who have been exposed to early-life adversity, which is a risk factor for psychological problems, allowing them to be monitored and guided towards preventive treatments, if necessary.

The origin of this study traces back several years, when senior author Erin C. Dunn, ScD, MPH, learned about work in the field of anthropology that could help solve a longstanding problem in her own research. Dunn is a social and psychiatric epidemiologist and an investigator in MGH’s Psychiatric and Neurodevelopmental Genetics Unit. She studies the effects of childhood adversity, which research suggests is responsible for up to one-third of all mental health disorders. Dunn is particularly interested in the timing of these adverse events and in uncovering whether there are sensitive periods during child development when exposure to adversity is particularly harmful. Yet Dunn notes that she and other scientists lack effective tools for measuring exposure to childhood adversity. Asking people (or their parents) about painful experiences in their early years is one method, but that’s vulnerable to poor recall or reluctance to share difficult memories. “That’s a hindrance for this field,” says Dunn.

However, Dunn was intrigued to learn that anthropologists have long studied the teeth of people from past eras to learn about their lives. “Teeth create a permanent record of different kinds of life experiences,” she says. Exposure to sources of physical stress, such as poor nutrition or disease, can affect the formation of dental enamel and result in pronounced growth lines within teeth, called stress lines, which are similar to the rings in a tree that mark its age. Just as the thickness of tree growth rings can vary based on the climate surrounding the tree as it forms, tooth growth lines can also vary based on the environment and experiences a child has in utero and shortly thereafter, the time when teeth are forming. Thicker stress lines are thought to indicate more stressful life conditions.

Dunn developed a hypothesis that the width of one variety in particular, called the neonatal line (NNL), might serve as an indicator of whether an infant’s mother experienced high levels of psychological stress during pregnancy (when teeth are already forming) and in the early period following birth.

To test this hypothesis, Dunn and two co-lead authors—postdoctoral research fellow Rebecca V. Mountain, PhD, and data analyst Yiwen Zhu, MS, who were both in the Psychiatric and Neurodevelopmental Genetics Unit at the time of the study—led a team that analyzed 70 primary teeth collected from 70 children enrolled in the Avon Longitudinal Study of Parents and Children (ALSPAC) in the United Kingdom. In ALSPAC (which is also called Children of the 90s), parents donated primary teeth (specifically, the pointed teeth on each side of the front of the mouth known as canines) that naturally fell out of the mouths of children aged 5 to 7. The width of the NNL was measured using microscopes. Mothers completed questionnaires during and shortly after pregnancy that asked about four factors that are known to affect child development: stressful events in the prenatal period, maternal history of psychological problems, neighborhood quality (whether the poverty level was high or it was unsafe, for instance), and level of social support.

Several clear patterns emerged. Children whose mothers had lifetime histories of severe depression or other psychiatric problems, as well as mothers who experienced depression or anxiety at 32 weeks of pregnancy, were more likely than other kids to have thicker NNLs. Meanwhile, children of mothers who received significant social support shortly after pregnancy tended to have thinner NNLs. These trends remained intact after the researchers controlled for other factors that are known to influence NNL width, including iron supplementation during pregnancy, gestational age (the time between conception and birth) and maternal obesity.

No one is certain what causes the NNL to form, says Dunn, but it’s possible that a mother experiencing anxiety or depression may produce more cortisol, the “stress hormone,” which interferes with the cells that create enamel. Systemic inflammation is another candidate, says Dunn, who hopes to study how the NNL forms. And if the findings of this research can be replicated in a larger study, she believes that the NNL and other tooth growth marks could be used in the future to identify children who have been exposed to early life adversity. “Then we can connect those kids to interventions,” says Dunn, “so we can prevent the onset of mental health disorders, and do that as early on in the lifespan as we possibly can.”