Regularly brushing your teeth and flossing could slash your risk of head and neck cancer, a promising new study has suggested. 

Research has long shown that high levels bacteria linked to gum disease can raise the likelihood of the condition as well as diabetes and high blood pressure.

But until now, experts did not know which specific bacteria lurking in people's mouths could be linked to head and neck cancer. 

US scientists discovered more than a dozen species that collectively they say raise the risk of head and neck squamous cell carcinoma — the most common type — by 50 per cent. 

Researchers argue their findings highlight the importance of good oral hygiene — often considered brushing teeth twice a day, flossing and regularly visiting the dentist. 

Surveys have shown, however, that just three in ten Brits floss daily. 

Study co-author and an expert in population health at New York University (NYU), Professor Richard Hayes, said: 'Our results offer yet another reason to keep up good oral-hygiene habits. 

'Brushing your teeth and flossing may not only help prevent periodontal disease, but also may protect against head and neck cancer.'

Study lead author Soyoung Kwak, a postdoctoral fellow in population health at NYU, added: 'Our findings offer new insight into the relationship between the oral microbiome and head and neck cancers.

'These bacteria may serve as biomarkers for experts to flag those at high risk.'

Around 12,400 new cases of head and neck cancers are diagnosed in the UK each year, with roughly 66,000 in the US.

But symptoms can be hard to spot, according to the NHS.

In the UK, cancer of the head or neck is the eighth most common, accounting for three per cent of all new cases.

There are more than 30 areas within the head and neck where tumours can develop.

Nine in 10 head and neck cancers start in squamous cells, Macmillan Cancer Support says. 

Squamous cells are flat, skin like cells that cover the lining of the mouth, nose, larynx, thyroid and throat.

Although most often diagnosed in older adults, oral cancers are becoming increasingly common in younger people. 

Doctors say human papillomavirus (HPV), a normally harmless virus that is spread sexually and through skin contact, could be behind the rise.

In the study, researchers analysed the diet, lifestyle and medical history data of almost 160,000 Americans. 

Volunteers were asked to rinse with mouthwash and provide saliva samples that were then preserved and tested for the number and types of microbes present. 

Over a follow up of 15 years, 236 participants were diagnosed with head and neck squamous cell carcinoma. 

Their oral microbe DNA was compared with 458 participants who had remained cancer-free. 

Factors that could skew the results, smoking history, age and alcohol intake were also accounted for. 

Writing in the journal JAMA Oncology, the researchers said 13 species of the hundreds of different bacteria routinely found in the mouth were found to raise or lower the risk of the cancer. 

This group was linked to a 30 per cent greater likelihood of developing the disease.   

In combination with five other species that are often seen in gum disease, the overall risk was increased by 50 per cent. 

However, they added that the study does not establish a direct link between bacteria and cancer. Instead it identifies a correlation. 

Study co-author and associate director for population research at its Perlmutter Cancer Center said: 'Now that we have identified key bacteria that may contribute to this disease, we next plan to explore the mechanisms that allow them to do so and in what ways we can best intervene.'