A research team from Harvard School of Public Health in Boston, MA, were the first to report strong evidence on a link between gum disease and pancreatic cancer, back in 2007.
The type of gum inflammation associated with pancreatic cancer in the study was periodontitis, which affects the tissue that support the teeth and can cause loss of bone around the base of the teeth.
The other main kind of gum disease - gingivitis; where the tissue around the teeth becomes inflamed - was not linked to increased cancer risk. However, gingivitis can lead to periodontitis if persistent. Gingivitis happens when bacteria in the plaque around the base of the teeth build up due to bad dental hygiene.
Examining data on gum disease from the Health Professionals Follow-Up Study, which involved a cohort of more than 51,000 men and began collecting data in 1986, the Harvard researchers found that men with a history of gum disease had a 64% increased risk of pancreatic cancer compared with men who had never had gum disease.
The greatest risk for pancreatic cancer among this group was in men with recent tooth loss. However, the study was unable to find links between other types of oral health problems - such as tooth decay - and pancreatic cancer.
The researchers suggest that there may be a link between high levels of carcinogenic compounds found in the mouths of people with gum disease and pancreatic cancer risk. They argue that these compounds - called nitrosamines - may react to the digestive chemicals in the gut in a way that creates an environment favorable to the development of pancreatic cancer.
However, a follow-up study from the team in 2012 was unable to prove whether the periodontitis bacteria are a cause or result of pancreatic cancer - the study could only prove that the two were linked.
"This is not an established risk factor," admitted author Dominique Michaud. "But I feel more confident that something is going on. It's something we need to understand better."