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Studies show e-cigarettes harmful to oral health

By Dental Tribune International
November 21, 2016

ROCHESTER, N.Y., USA/QUEBEC CITY, Canada: Electronic cigarettes continue to grow in popularity among young adults and current and former smokers because they are often perceived as a healthier alternative to conventional cigarettes. However, two recent studies by scientists in the U.S. and Canada have found that regular exposure to e-cigarette vapors causes damage to the gingival tissue, which may lead to infection, inflammation and periodontal disease.

Both studies investigated the effect of e-cigarettes on oral health on cellular and molecular levels through in vitro experiments. The team of Prof. Mahmoud Rouabhia from the Faculty of Dentistry at Université Laval in Quebec City exposed gingival epithelial cells to e-cigarette vapor, finding that a large number of these cells died within a few days. “Mouth epithelium is the body’s first line of defense against microbial infection,” Rouabhia explained. “This epithelium protects us against several microorganisms living in our mouths.”

To simulate what happens in a person’s mouth while inhaling, the Canadian researchers placed human epithelial cells into a small chamber containing a saliva-like liquid. E-cigarette vapor was pumped into the chamber at a rate of two 5-second “inhalations” per minute for 15 minutes a day. Observations under the microscope showed that the percentage of dead or dying cells, which is about 2 percent in unexposed cell cultures, rose to 18, 40 and 53 percent after one, two and three days of exposure to e-cigarette vapor, respectively.

“Contrary to what one might think, e-cigarette vapor isn’t just water,” Rouabhia stated. “Although it doesn’t contain tar compounds like regular cigarette smoke, it exposes mouth tissues and the respiratory tract to compounds produced by heating the vegetable glycerin, propylene glycol, and nicotine aromas in e-cigarette liquid.”

The cumulative effects of this cell damage have not yet been documented, but they are worrying, according to Rouabhia. “Damage to the defensive barrier in the mouth can increase the risk of infection, inflammation, and gum disease. Over the longer term, it may also increase the risk of cancer. This is what we will be investigating in the future,” he concluded.

Researchers at the University of Rochester Medical Center in the U.S. came to similar conclusions. Dr. Irfan Rahman, Professor of Environmental Medicine at the university’s School of Medicine and Dentistry, and his colleagues exposed cell cultures of human gingival epithelial cells and periodontal ligament fibroblasts to e-cigarette vapors. “We showed that when the vapors from an e-cigarette are burned, it causes cells to release inflammatory proteins, which in turn aggravate stress within cells, resulting in damage that could lead to various oral diseases,” he explained.

Most e-cigarettes feature a battery, a heating device and a cartridge to hold liquid, which typically contains nicotine, flavorings and other chemicals. The U.S. researchers found that the flavoring chemicals negatively affect gingival cells too. “We learned that the flavorings—some more than others—made the damage to the cells even worse,” said study author Fawad Javed, a postdoctoral resident at Eastman Institute for Oral Health, part of the university’s medical center.

“More research, including long term and comparative studies, are needed to better understand the health effects of e-cigarettes,” concluded Rahman, who would like to see manufacturers disclose all of the materials and chemicals used, so that consumers can be made aware of the potential dangers of e-cigarette smoking.

The study conducted by the U.S. researchers is titled “E-cigarettes and flavorings induce inflammatory and pro-senescence responses in oral epithelial cells and periodontal fibroblasts” and was published online on Oct. 24 in the Oncotarget journal.

The study by the Canadian research team, titled “E-cigarette vapor induces an apoptotic response in human gingival epithelial cells through the caspase-3 pathway,” was published online on Nov. 3 in the Journal of Cellular Physiology.

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