Oral bacteria that cause dental diseases are associated with Alzheimer's disease, a new study has found.

According to a latest research, Lipopolysaccharide, a component of Porphyromonas gingivalis was present in four of ten Alzheimer disease patients. P. Gingivalis triggers a kind of immune response in the mouth that leads to loss of oral bone.

Previous studies have shown that the oral pathogen is associated with increased risk of atherosclerosis and even erectile dysfunction.

 In the present study, scientists found the bacterium only in people with AD.

"This clearly shows that there is an association between oral bacteria and Alzheimer's disease, but not causal association," Lakshmyya Kesavalu, from University of Florida College of Dentistry, one of the study, said in a news release.

Bacteria that cause an infection in the mouth can get into the bloodstream via chewing, brushing and flossing. Researchers believe that these bacteria reach the brain via blood and begin growing there, which leads to loss of brain tissue.

The study is published in the Journal of Alzheimer's Disease.

A related study conducted by researchers at the University of Florida had found that the bacterium can enter brains of mice through the bloodstream. In the unpublished study, experts had infected lab mice with four different types of bacteria that cause dental diseases in humans.

On a related note, about 47.2 percent of adults in the U.S. have some form of periodontal disease, according to "Prevalence of Periodontitis in Adults in the United States: 2009 and 2010."

Periodontal disease is the infections of gums and bones that support the teeth. In the early stages the disease is called gingivitis. Later, as the disease progresses, the gums become red, swollen and even bleed.