New research in the UK has shown that people who fail to brush their teeth twice a day have a higher chance of heart disease.
The link between gum disease and heart problems is already known but experts have now been able to measure the effect of daily brushing.
A new study found that people who never or rarely brush their teeth are 70% more likely to suffer heart disease as those who brush twice a day.
However, the overall risk from poor oral hygiene remains quite low, they said.
Experts from University College London analysed data for more than 11,000 people with an average age of 50 taking part in the Scottish Healthy Survey.
They looked at people's brushing habits as well as their lifestyles, such as whether they smoked or took exercise.
People were asked how often they visited their dentist (at least once every six months, every one to two years, or rarely/never) and how often they brushed their teeth (twice a day, once a day or less than once a day).
Separate details were collected on people's medical histories, blood pressure, and their family's history of heart disease. Blood samples were also taken to measure markers of inflammation in the blood.
Just over six out of 10 (62%) people visited their dentist every six months while 71% said they brushed their teeth twice a day.
During eight years of follow-up, there were 555 examples of serious heart problems, mostly caused by heart disease, including heart attacks. Of these, 170 were fatal.
The experts found that people who never or rarely brushed their teeth were 70% more likely to suffer heart disease than those who brushed twice a day.
This held true even when factors likely to influence the results, such as obesity and smoking, were taken into account.
Poor oral hygiene was also linked to low-grade inflammation in the blood.
Writing online in the British Medical Journal, author Professor Richard Watt said: 'Our results confirmed and further strengthened the suggested association between oral hygiene and the risk of cardiovascular disease.
'Furthermore inflammatory markers were significantly associated with a very simple measure of poor oral health behaviour.
'Future experimental studies will be needed to confirm whether the observed association between oral health behaviour and cardiovascular disease is in fact causal or merely a risk marker.'
Judy O'Sullivan, senior cardiac nurse at the British Heart Foundation, said: 'If you don't brush your teeth, your mouth can become infected with bacteria which can cause inflammation.
'It is already known that there is a link between inflammation and a higher risk of developing heart disease.
'However, it is complicated by the fact that poor oral hygiene is often associated with other well-known risk factors for heart disease, such as smoking and poor diet.
'Good personal hygiene is a basic element of a healthy lifestyle.
'But if you want to help your heart, you should eat a balanced diet, avoid smoking and take part in regular physical activity.'