Having more than one dental x-ray a year can double or even triple the chance of developing a common type of brain tumour, according to an American study.
Researchers found people who recalled having frequent dental x-rays were more likely than those who did not, to have a form of non-spreading cancer called meningioma.
These tumours grow in the lining inside the skull. Most are slow growing but they can cause problems if they start to press on the brain, and they can be lethal.
Academics at Yale University School of Medicine in New Haven, Connecticut, and the Brigham and Women's Hospital in Boston, Mass., looked at two types of head x-ray, called "bitewing" and Panorex.
In the study of almost 3,000 adults, about half diagnosed with the disease and half not, they found frequent doses of x-ray radiation were linked with more cases of the cancer.
Specifically, people who remembered having Panorex examinations once a year or more were 2.7 to 3.0 times more likely, depending on age, to have developed meningioma than those who did not.
Those who remembered having bitewing x-rays on at least a yearly basis, were at a 40 to 90 per cent raised risk.
Study author Dr Elizabeth Claus, said she hoped the research would serve "to increase awareness regarding the optimal use of dental x-rays".
Dr Paul Pharoah, a reader in cancer epidemiology at Cambridge University, said: "The authors report that dental x-rays are associated with a small relative increase in risk of disease of approximately 50 percent or 1.5-fold. This finding is statistically significant.
"However, as the disease is rare, the increase in absolute risk is tiny - the lifetime risk increasing from 15 in every 10,000 people to 22 in 10,000."