A 4-year, $2.2 million grant has been awarded to the University of North Carolina (UNC) by the National Institute of Dental Research to better define the link between periodontal (gum) disease and heart disease. This is the largest study of its kind enabling researchers to explore in detail the underlying inflammatory responses common to both diseases.

By tapping into the ongoing Atherosclerosis Risk in Communities Study (ARIC) sponsored by the National Heart, Lung and Blood Institute, UNC researchers will be able to examine markers of periodontal disease in 14,000 individuals already receiving extensive heart disease testing through the ARIC study. The dental researchers will then compare these periodontal markers with clinical measures of heart disease; the occurrence of heart attacks, stroke, and death; and ultrasound measures of carotid vessel thickening. The researchers hope that these comparisons will uncover the biological association between dental disease and heart disease.

Bacteria Implicated
Several previous studies, including smaller ones conducted by the UNC researchers, have shown that individuals with severe periodontal disease are more likely to develop heart disease than are people without gum problems. One study even suggested that individuals with severe periodontal bone loss (loss of bone that holds the teeth in place) may have twice the risk of fatal coronary heart disease as normal individuals, after controlling for other relevant risk factors.

Part of the link between periodontal disease and heart disease may lie with harmful bacteria that colonize the mouth. The investigators theorize that certain types of these bacteria, which clump together in sticky masses called plaque and cause periodontal diseases, also activate white blood cells in the body to release harmful clotting factors and proteins (called pro-inflammatory mediators) that contribute to heart disease and stroke.

"Establishing periodontal diseases as a risk factor for heart disease and stroke would take on new meaning for oral health as it relates to the overall health of individuals," according to Drs. James D. Beck and Steven Offenbacher, principal and co-principal investigators of the study. Dr. Beck is the Kenan professor and chair of the Department of Dental Ecology at the UNC School of Dentistry; Dr. Offenbacher is a professor of periodontology at the UNC School of Dentistry and a member of the graduate faculty.

Comparison of Disease Markers
The UNC researchers will look at several measures of periodontal disease and biological responses in ARIC study participants. First, they will measure participants' periodontal pocket depth (spaces where unhealthy gums have pulled away from the teeth) and attachment loss (loss of tissues holding the teeth in place). The researchers also will collect samples of gingival crevicular fluid, the fluid that seeps from gums around the base of the teeth. The fluid will be analyzed to see if it contains the same inflammation-provoking substances associated with heart disease. Finally, blood samples will be collected to be analyzed later for antibodies to periodontal bacteria.

With this information in hand, the researchers will compare these periodontal measures and responses to known risk factors for heart disease, such as elevated levels in the blood of fat (lipids) and clotting factors. They will determine whether severe narrowing of the arteries, as well as elevated lipid levels and clotting factors, are associated with high levels of pro-inflammatory mediators in gingival crevicular fluid.

Participants in the periodontal/heart disease study reside in four communities: Forsyth County, NC; Jackson, MS; Minneapolis, MN; and Washington County, MD. They range in age from 45-64 years and are of various ethnic backgrounds.

Working with Drs. Beck and Offenbacher on the periodontal part of the study at UNC are Drs. Gerardo Heiss, Herman Tyroler and Gary Koch from the UNC School of Public Health, and Frances Smith, from the UNC Dental Research Center. The following institutions are also collaborating with UNC on the study: Wake Forest University; the Bowman Gray School of Medicine, Public Health Science; the University of Minnesota School of Public Health, Division of Epidemiology; the University of Mississippi Medical Center, Department of Medicine; and The Johns Hopkins School of Hygiene and Public Health.