<p id="first" class="lead" style="font-size: 18px; border-radius: 0px !important;">A series of new studies by researchers at NYU College of Dentistry highlights how e-cigarettes alter oral health and may be contributing to gum disease. The latest, published in&nbsp;<em style="border-radius: 0px !important;">mBio</em>, finds that e-cigarette users have a unique oral microbiome -- the community of bacteria and other microorganisms -- that is less healthy than nonsmokers but potentially healthier than cigarette smokers, and measures worsening gum disease over time.</p><div id="text" style="border-radius: 0px !important;"><p style="border-radius: 0px !important;">"To our knowledge, this is the first longitudinal study of oral health and e-cigarette use. We are now beginning to understand how e-cigarettes and the chemicals they contain are changing the oral microbiome and disrupting the balance of bacteria," said Deepak Saxena, who led the research with Xin Li; both are professors of molecular pathobiology at NYU College of Dentistry.</p><p style="border-radius: 0px !important;">Gum disease affects nearly half of U.S. adults over 30 years of age. Smoking cigarettes is a known risk factor for developing gum disease, but less is known about the impact of e-cigarettes -- which vaporize nicotine and other chemicals -- on oral health, especially the long-term consequences of vaping.</p><p style="border-radius: 0px !important;">The researchers studied the oral health of 84 adults from three groups: cigarette smokers, e-cigarette users, and people who have never smoked. Gum disease was assessed through two dental exams six months apart, during which plaque samples were taken to analyze the bacteria present.</p><p style="border-radius: 0px !important;"><strong style="border-radius: 0px !important;">Changes to gum health</strong></p><p style="border-radius: 0px !important;">All participants had some gum disease at the start of the study, with cigarette smokers having the most severe disease, followed by e-cigarette users. After six months, the researchers observed that gum disease had worsened in some participants in each group, including several e-cigarette users.</p><p style="border-radius: 0px !important;">A key indicator of gum disease is clinical attachment loss, measured by gum ligament and tissue separating from a tooth's surface, leading the gum to recede and form pockets. These pockets are breeding grounds for bacteria and can lead to more severe gum disease. In a study of the same participants published in&nbsp;<em style="border-radius: 0px !important;">Frontiers in Oral Health</em>, the research team found that clinical attachment loss was significantly worse only in the e-cigarette smokers -- not non-smokers and cigarette smokers -- after six months.</p><p style="border-radius: 0px !important;"><strong style="border-radius: 0px !important;">A unique microbiome</strong></p><p style="border-radius: 0px !important;">The researchers then analyzed the bacteria found in the plaque samples and determined that e-cigarette users have a different oral microbiome from smokers and nonsmokers -- building on findings the team previously reported in&nbsp;<em style="border-radius: 0px !important;">iScience</em>&nbsp;and&nbsp;<em style="border-radius: 0px !important;">Molecular Oral Microbiology</em><em style="border-radius: 0px !important;">.</em></p><p style="border-radius: 0px !important;">While all groups shared roughly a fifth of the types of bacteria, the bacterial makeup for e-cigarette users had strikingly more in common with cigarette smokers than nonsmokers. Several types of bacteria, including&nbsp;<em style="border-radius: 0px !important;">Selenomonas</em>,&nbsp;<em style="border-radius: 0px !important;">Leptotrichia,&nbsp;</em>and&nbsp;<em style="border-radius: 0px !important;">Saccharibacteria</em>, were abundant in both smokers and vapers compared to nonsmokers. Several other bacteria -- including&nbsp;<em style="border-radius: 0px !important;">Fusobacterium</em>&nbsp;and&nbsp;<em style="border-radius: 0px !important;">Bacteroidales</em>, which are known to be associated with gum disease -- were particularly dominant in the mouths of e-cigarette users.</p><p style="border-radius: 0px !important;">When plaque samples were gathered and analyzed in the six-month follow-up, the researchers found greater diversity in bacteria for all groups studied, yet each group maintained its own distinct microbiome.</p><p style="border-radius: 0px !important;">"Vaping appears to be driving unique patterns in bacteria and influencing the growth of some bacteria in a manner akin to cigarette smoking, but with its own profile and risks to oral health," said Fangxi Xu, a junior research scientist in Saxena's lab and the study's co-first author.</p><p style="border-radius: 0px !important;"><strong style="border-radius: 0px !important;">An altered immune response</strong></p><p style="border-radius: 0px !important;">The researchers found that the distinct microbiome in e-cigarette users was correlated with clinical measures of gum disease and changes to the host immune environment. In particular, vaping was associated with different levels of cytokines -- proteins that help regulate the immune system. Certain cytokines are linked to an imbalance in oral bacteria and can worsen gum disease by making people prone to inflammation and infection.</p><p style="border-radius: 0px !important;">TNFα, a cytokine that causes inflammation, was significantly elevated among e-cigarette users. In contrast, cytokines IL-4 and IL-1β were lower among e-cigarette users; IL-4 tends to be reduced in people with gum disease and increases after treatment, which suggests that certain bacteria in the mouths of e-cigarette users may be actively suppressing immune responses.</p><p style="border-radius: 0px !important;">The researchers concluded that the distinct oral microbiome of e-cigarette users elicits altered immune responses, which along with clinical markers for gum disease illustrate how vaping presents its own challenge to oral health.</p><p style="border-radius: 0px !important;">"E-cigarette use is a relatively new human habit," said Scott Thomas, an assistant research scientist in Saxena's lab and the study's co-first author. "Unlike smoking, which has been studied extensively for decades, we know little about the health consequences of e-cigarette use and are just starting to understand how the unique microbiome promoted by vaping impacts oral health and disease."</p><p style="border-radius: 0px !important;">This research was supported by the National Institute of Dental &amp; Craniofacial Research (DE025992, DE027074), the National Cancer Institute (CA206105), and the NYU Mega-Grants Initiative. The study included additional collaborators from NYU College of Dentistry, NYU Grossman School of Medicine, and the University of Pennsylvania.</p></div>