Parents may tell their children that proper flossing and brushing twice a day for at least two minutes helps reduce dental plaque and may help prevent cavities and gum disease.
But much more is at stake.
Results from a study funded by the National Cancer Institute and published in Cancer Research, a journal of the American Association for Cancer Research (AACR), shows that some types of bacteria present in the mouth lead to periodontal disease are also associated with higher risk of esophageal cancer. 
“Esophageal cancer is the eighth most common cancer and the sixth leading cause of cancer death worldwide,” noted Jiyoung Ahn, Ph.D, an associate professor and associate director for population science at the Laura and Isaac Perlmutter Center at NYU Langone Health in New York, New York (USA), and lead author of the study.
Because the Esophageal cancer is often not discovered until it has reached an advanced stage, five-year survival rates range from about 15 to 25% worldwide.
“Esophageal cancer is a highly fatal cancer, and there is an urgent need for new avenues of prevention, risk stratification, and early detection,” Ahn explained.
Previous research has shown that periodontal disease caused by certain oral microbiota has been associated with several types of cancer, including oral and head and neck cancers.
In order to determine whether oral microbiota were associated with subsequent risk of esophageal adenocarcinoma (EAC) or esophageal squamous cell carcinoma (ESCC), Ahn and colleagues collected oral wash samples from 122,000 participants in two large health studies: the National Cancer Institute Prostate, Lung, Colorectal, and Ovarian Cancer Screening Trial and the American Cancer Society Cancer Prevention Study II Nutrition cohort.
In 10 years of follow-up, 106 participants developed esophageal cancer. In a prospective case-control study, the researchers extracted DNA and sequenced oral wash samples, allowing researchers to compare the oral microbiomes of the esophageal cancer cases and the cancer-free cases.
Certain bacteria types were associated with higher risk of esophageal cancer. For example, higher levels of the Tannerella forsythia bacteria, an anaerobic, Gram-negative bacterial species of the Cytophaga-Bacteroidetes family and a member of the red complex of periodontal pathogens, have been implicated in periodontal diseases and was associated with a 21% increased risk of EAC.
The bacteria Porphyromonas gingivalis, which belongs to the phylum Bacteroidetes and is a nonmotile, Gram-negative, rod-shaped, anaerobic, pathogenic bacterium, was associated with a higher risk of ESCC.
“Both species of bacteria are linked with common gum disease,” Ahn noted.
The study also showed that a few types of oral bacteria were associated with lower risk of esophageal cancer.
For example, the researchers found that depletion of the commensal genus Neisseria and the species Streptococcus pneumoniae were associated with lower EAC risk.
“This indicates that certain bacteria may have a protective effect, and future research could potentially examine whether these bacteria could play a role in preventing esophageal cancer,” Ahn said.
“Our study indicates that learning more about the role of oral microbiota may potentially lead to strategies to prevent esophageal cancer, or at least to identify it at earlier stages,” Ahn said. “The next step is to verify whether these bacteria could be used as predictive biomarkers.”
“The study result confirms that good oral health, including regular tooth brushing and dental visits, is an important way to guard against periodontal disease and the growing list of health conditions associated with it,” Ahn added
The study’s primary limitation is that the researchers did not have complete information on the participants’ oral health. Therefore, they could not determine whether the presence of pathogens was enough to affect esophageal cancer risk, or whether full-blown periodontal disease was the risk factor.
Precancerous lesions of gastric cancer
Results from an unrelated and uncontrolled experiment designed to prove whether or how oral health problems may contribute to stomach cancer, published in the November 2017 edition of the Journal of Periodontology, showed that, compared with the control group, patients with precancerous lesions of gastric cancer, also known as PLGC, experienced higher prevalence of bleeding on probing (31.5% versus 22.4%; P <0.05), higher levels of Treponema denticola (P <0.01) and Aggregatibacter actinomycetemcomitans (P <0.01), and less bacterial diversity in their saliva (P <0.01).
The researchers used a multivariate logistic regression model consisting of all key sociodemographic characteristics, oral health behavioral factors, and periodontal assessments. The results revealed that elevated colonization with periodontal pathogens, specifically Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola, and Aggregatibacter actinomycetemcomitans, decreased bacterial diversity in dental plaque.
The study confirmed that not flossing teeth regularly was a significant predictor of increased risk of precancerous lesions of gastric cancer (P = 0.022).
“The their evidence suggests that periodontal pathogen burdens and bacterial diversity in the oral cavity are important factors contributing to a potentially increased risk of developing precancerous gastric lesions,” Yihong Li, Professor of Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, and the corresponding author of the study, noted.
Based on the available evidence, the researchers observed that periodontal disease may cause inflammation in the mouth and, over time, contribute to inflammation throughout the body since various bacteria in the mouth may travel to the gastrointestinal track.
“And while periodontal pockets may often be hard to access by a regular toothbrush and, as a result, could serve as a reservoir of bacterial colonization, maintaining proper, thorough, oral hygiene through teeth brushing, flossing and regular, bi-annual, visits to your dentist may indeed be prudent,” Li concluded.
And that that’s not just good advice for children…
Last Editorial Review: December 14, 2017
Featured Image:Woman and dentist Courtesy: © 2017 Todd Buchanan/American Society of Hematology | Used with permission. Photo 1.0 Jiyoung Ahn, Ph.D, an associate professor and associate director for population science at the Laura and Isaac Perlmutter Center at NYU Langone Health in New York, New York (USA) Courtesy: © 2017 Laura and Isaac Perlmutter Center at NYU Langone Health | Used with permission.
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