Gastroesophageal reflux disease, or GERD, is when stomach acid backs up into the esophagus. The condition is common, affecting about 15% of people at some time in their lives. Although most people with reflux symptoms have minor problems, there is a subgroup of people with GERD who experience chronic, severe pain, trouble swallowing, or a hiatal hernia (a hole in the diaphragm that allows food and acid to flow back into the stomach). These patients are considered to have reflux esophagitis.

Reflux esophagitis, like periodontitis, is associated with obesity. Both conditions tend to be more common in people who are overweight. “Fat pads between the diaphragm and chest wall expand, so the esophagus is pushed upward and out of the way of the stomach,” explains Dr. Richard Kravitz, M.D., clinical professor of otolaryngology at the University of Michigan. The result is a more acidic environment in the esophagus, which encourages bacteria growth and increases the chance of developing reflux esophagitis.

It’s no surprise that people with GERD are more likely to develop periodontitis. The same thing happens when people with periodontitis develop GERD.

Cram says there are two theories on how this works. One is that GERD increases the amount of acid in the mouth, which weakens tooth enamel and promotes gum disease. The other theory is that inflammation from gum disease can irritate the esophagus, making it more likely to produce acid.

The connection between GERD and periodontitis is even stronger among smokers. While periodontitis isn’t a major cause of smoking cessation, a recent study published in the Journal of Dental Research showed that quitting may actually improve GERD.