Poor dental hygiene increases your risk of heart attacks and strokes according to two studies out this week, reports Agence France-Presse.

The number one killer in the world is heart disease, extinguishing 17 million lives every year according to World Health Organisation figures, and it is the leading cause of death in the US, England, Canada, Wales and New Zealand, where it accounts for 40 per cent of all deaths annually – 11,300 people.

While obesity, high cholesterol and smoking are the primary causes, the new studies show dirty mouths can be added to the list.

Howard Jenkins of the University of Bristol in Britain says, "We now recognise that bacterial infections are an independent risk factor for heart diseases. In other words, it doesn't matter how fit, slim or healthy you are, you're adding to your chances of getting heart disease by having bad teeth."

If you don’t brush your teeth, there are up seven hundred different bacteria in your mouth that will be grateful for your laziness.

Many are essential to good health, and some are benign. Others – not so much. The new studies argue they can lead to diseases of the arteries linked to heart attack and stroke.

Steve Kerrigan of the Royal College of Surgeons says, "The mouth is probably the dirtiest place in the human body. If you have an open blood vessel from bleeding gums, bacteria will gain entry to your bloodstream."

Once in, some bacteria attach to cell ‘platelets’, making them clot and reduce blood flow.

"We mimicked the pressure inside the blood vessels and in the heart, and demonstrated that bacteria use different mechanisms to cause platelets to clump together, allowing them to completely encase the bacteria," says Kerrigan - which also shields the bacteria from immune system cells and antibiotics.

The second study, led by Greg Seymour of the University of Otago in Dunedin, explains how mouth bacteria can stimulate atherosclerosis, which hardens your arteries.

All organisms produce ‘stress proteins’ which happen under conditions of inflammation, starvation, toxins or oxygen deprivation, and one function of stress proteins is guiding other proteins across cell walls.

However, they also attach to foreign objects, or antigens, delivering them to immune cells, which provokes an immune system reaction.

While the body doesn’t usually attack its own stress proteins, the similarity of bacterial stress proteins means they do trigger a reaction, and the immune system can’t differentiate between the two once that occurs, says Seymour.

"White blood cells can build up in the tissue of arteries, causing atherosclerosis," he explained in a phone interview to AFP.