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Release: Oct. 10, 2000

UI College of Dentistry research finds link between health of jaw, other bones

IOWA CITY, Iowa -- For years, researchers have studied the relationship between bone density in the jaws and elsewhere in the body. A new study conducted at the University of Iowa College of Dentistry offers evidence that bone changes in the jaw parallel those found in other bones during normal aging.

Karin Southard, D.D.S., UI professor of orthodontics, said the study is one of few to focus on alveolar process bone, or the portions of the jaws where tooth sockets are located. She added that further research may show whether bone changes in these areas are connected to tooth loss.

"Some people lose more bone with age. They may be more susceptible to periodontal disease due to this loss," she said. Periodontal disease affects the supporting structures of teeth, including bone, gums and other tissues.

Southard’s study, published earlier this year in the Journal of Dental Research, is also unique in its emphasis on the upper jaw, or the maxilla. Previous work had concentrated on the lower jaw, or mandible, because it is larger and easier to study. However, the mandible also is made up primarily of thick cortical bone that is relatively slow to show changes in density. Studies that looked to the mandible for signs of change throughout the skeletal system yielded mixed results.

In contrast, Southard and her colleagues found significant relationships between the density of the maxillary alveolar process and the lumbar spine, the hip and the radius bone in the forearm. They did not find the same relationships between the mandible and other bones.

Unlike the mandible, the maxillary alveolar process is composed of more trabecular bone, a type of bone that degenerates more rapidly. Thus this region may be a good indicator of bone loss in other parts of the body.

The investigators studied 41 women between the ages of 20 and 78 using X-rays of the jaws and other bones. In addition to relationships between bones, they found a significant decline in alveolar process bone density with age effect of normal aging. Lower levels of the hormone estrogen also can contribute to the decline of bone density in women.

Southard said some studies have shown that hormone replacement therapy may reduce the risk of tooth loss, a finding that is noted in advertisements for hormone-replacing drugs. Whether tooth loss is caused by hormone-related or age-related changes in alveolar process bone remains to be proven.

Southard became interested in the relationship between bone density and tooth movement as a graduate student. She has teamed with her husband, Tom Southard, D.D.S., also a UI professor of orthodontics and an electrical engineer, to study the phenomenon. He developed the software used in their analysis.

Karin Southard hopes to see additional research using larger population samples confirm her work and further probe the role of bone density in tooth loss. Her research uses specialized equipment and techniques, so she doesn’t expect to see general dentists diagnosing bone loss using regular dental X-rays.

However, her work gives researchers guidance for further studies that may shed new light on periodontal disease and whether dental regions can be early indicators of disease throughout the skeletal system. It also provides more evidence that the mouth is a window to disorders that affect the entire body.