Poor oral hygiene may increase risk of cancer death, scientists claim.
An increased amount of dental plaque has been linked to premature cancer death by researchers in Sweden.
An observational study, published in the BMJ Open online journal, examined 1,390 people between 1985 and 2009.
At the start of the research, all participants were quizzed on factors likely to increase their cancer risk. Their mouth hygiene was also assessed.
After 24 years, 58 patients had died -- 35 as a result of cancer. Those who died had a significantly higher amount of dental plaque than survivors, researchers discovered.
The dental plaque index in those who had died was higher than those who had survived.
Those who died scored between 0.84 to 0.91 on the index -- indicating that the gum area of the teeth had been covered with plaque.
The survivors had consistently lower scores of 0.66 to 0.67 -- indicating only partial plaque coverage.
The average age of death was 61 for the women and 60 for the men.
The women would have been expected to live around 13 years longer, and the men an additional 8.5 years, so their deaths could be considered premature, say the authors.
But the authors also say their findings do not prove dental plaque causes or definitely contributes to cancer and call for further research.
The authors wrote: "Our study hypothesis was confirmed by the finding that poor (mouth) hygiene, as reflected in the amount of dental plaque, was associated with increased cancer mortality."
"Further studies are required to determine whether there is any causal element in the observed association."
Dental plaque, which indicates poor oral hygiene and is a potential source of infections, has previously been implicated in systemic health problems.
It is made up of a film of bacteria, which covers the surfaces of the teeth and gaps between the teeth and gums.