Men who don't brush their teeth twice a day are almost three times as likely to suffer from erectile dysfunction, a study has found.
Gum disease - caused by not brushing - is thought to boost the odds of damaging the blood vessels which supply the penis.
A review of studies involving more than 200,000 men has strengthened a direct link between the two conditions, experts claim.
The research adds to growing evidence poor oral hygiene can impact a man's performance in the bedroom and potentially have other health consequences.
Scientists at Jinan University in China reviewed five studies on the link between periodontal disease (gum disease) and erectile dysfunction.
They found men with gum disease – triggered by bad oral hygiene – are 2.85 times more likely to struggle to get an erection.
Both conditions are common – almost all adults have some degree of gum damage, according to the NHS, but it can worsen and become a health concern if not treated.
Experts recommend people brush their teeth twice a day with fluoride toothpaste and clean between their teeth daily with floss or inter-dental brushes.
And 'most men' over the age of 40 will have episodes of erectile dysfunction, known as impotence, although it can affect men at any age.
Impotence is when men struggle or fail to maintain a firm enough erection to have sex – it can be temporary or long-lasting, and have physical or mental causes.
Scientists believe erectile dysfunction and gum disease are linked because they're both caused by the same type of inflammation in the blood vessels.
This inflammation can be triggered by a molecule called CRP, which is found in higher-than-normal levels in both impotent men and those with gum disease.
CRP is also elevated in men with heart disease, suggesting it begins by damaging smaller blood vessels before affecting major organs.
A study published last year by the University of Granada in Spain found the same connection between oral health and sexual performance.
Researchers there did the first study of the connection in European men and found impotence risk was almost double in men who didn't take care of their teeth.
Almost three quarters of men – 74 per cent – who already had trouble in the bedroom also had gum disease.
However, only 58 per cent of the men without erection trouble had the oral health problem.
CEO of dental charity the Oral Health Foundation, Dr Nigel Carter, said at the time: 'This may turn out to be a wake-up call for men to start paying greater attention to their oral health, particularly their gums.
'In recent years, gum disease has been linked with conditions like diabetes, stroke and heart disease.
'But an increased risk of coming up short in the bedroom may be the final straw for men who might have been reluctant to spend a little extra time looking after their gums.'
The Jinan University study was published in the Journal of Sexual Medicine.