Bacterium that causes gum disease packs a 1-2 punch to the jaw

The newly discovered bacterium that causes gum disease delivers a one-two punch by also triggering normally protective proteins in the mouth to actually destroy more bone, a University of Michigan study found.

Scientists and oral health care providers have known for decades that bacteria are responsible for periodontitis, or gum disease. Until now, however, they hadn't identified the bacterium.

"Identifying the mechanism that is responsible for periodontitis is a major discovery," said Yizu Jiao, a postdoctoral fellow at the U-M Health System, and lead author of the study appearing in the recent issue of the journal Cell Host and Microbe.

Jiao and Noahiro Inohara, research associate professor at the U-M Health System, worked with William Giannobile, professor of dentistry, and Julie Marchesan, formerly of Giannobile's lab.

The study yielded yet another significant finding: the bacterium that causes gum disease, called NI1060, also triggers a normally protective protein in the oral cavity, called Nod1, to turn traitorous and actually trigger bone-destroying cells. Under normal circumstances, Nod1 fights harmful bacterium in the body.

"Nod1 is a part of our protective mechanisms against bacterial infection. It helps us to fight infection by recruiting neutrophils, blood cells that act as bacterial killers," Inohara said. "It also removes harmful bacteria during infection. However, in the case of periodontitis, accumulation of NI1060 stimulates Nod1 to trigger neutrophils and osteoclasts, which are cells that destroy bone in the oral cavity."

Giannobile, who also chairs the Department of Periodontics and Oral Medicine at the U-M School of Dentistry, said understanding what causes gum disease at the molecular level could help develop personalized therapy for dental patients.

"The findings from this study underscore the connection between beneficial and harmful bacteria that normally reside in the oral cavity, how a harmful bacterium causes the disease, and how an at-risk patient might respond to such bacteria," Giannobile said.

Consuming cheese may help protect teeth against cavities

Consuming dairy products is vital to maintaining good overall health, and it's especially important to bone health. But there has been little research about how dairy products affect oral health in particular. However, according to a new study published in the May/June 2013 issue of General Dentistry, the peer-reviewed clinical journal of the Academy of General Dentistry (AGD), consuming cheese may help protect teeth against cavities.

The study sampled 68 subjects ranging in age from 12 to 15, and the authors looked at the dental plaque pH in the subjects' mouths before and after they consumed cheese, milk, or sugar-free yogurt. A pH level lower than 5.5 puts a person at risk for tooth erosion, which is a process that wears away the enamel (or protective outside layer) of teeth. "The higher the pH level is above 5.5, the lower the chance of developing cavities," explains Vipul Yadav, MDS, lead author of the study.

The subjects were assigned into groups randomly. Researchers instructed the first group to eat cheddar cheese, the second group to drink milk, and the third group to eat sugar-free yogurt. Each group consumed their product for three minutes and then swished with water. Researchers measured the pH level of each subject's mouth at 10, 20, and 30 minutes after consumption.

The groups who consumed milk and sugar-free yogurt experienced no changes in the pH levels in their mouths. Subjects who ate cheese, however, showed a rapid increase in pH levels at each time interval, suggesting that cheese has anti-cavity properties.

The study indicated that the rising pH levels from eating cheese may have occurred due to increased saliva production (the mouth's natural way to maintain a baseline acidity level), which could be caused by the action of chewing. Additionally, various compounds found in cheese may adhere to tooth enamel and help further protect teeth from acid.

"It looks like dairy does the mouth good," says AGD spokesperson Seung-Hee Rhee, DDS, FAGD. "Not only are dairy products a healthy alternative to carb- or sugar-filled snacks, they also may be considered as a preventive measure against cavities."