For more than a century, the dental and medical fields acted independently of each other, says Dr. Euan Swan, manager of dental programs at the Canadian Dental Association, but that's changed in recent years.

"Now there's a better understanding from both sides that what goes on in your mouth might affect other parts of your body and vice versa," says Swan.

Here are five ailments that are connected to unhealthy oral habits.

Oral cancer
Oral cancer affects the soft tissues of the mouth, meaning your tongue, your lips, the lining and floor of your mouth, and the inside of your cheeks. If left untreated, it can spread to the rest of your body.

If oral cancer is not looked after early on, the eventual treatment may lead to facial disfigurement, says Swan. "You can lose portions of your jaw and it can have quite an impact on an individual's overall health and quality of life," he explains.

Your risk of oral cancer increases if you use tobacco (whether smoking or chewing), if you abuse alcohol and if you are infected with human papillomavirus.

Diabetes
Studies have shown a definitive two-way relationship between gum disease and diabetes.

A person with diabetes has high blood sugar and "if you have gum disease, it's harder to control your diabetes because the chronic inflammation in your mouth is a challenge for your body in terms of controlling its metabolism of sugar," says Swan.

Prevent gum disease by practising good oral hygiene habits, including brushing your teeth twice a day, flossing once a day and visiting your dentist for regular checkups.

Heart disease
Despite studies that have made associations between bad oral hygiene and heart disease, there is no definitive "cause and effect" between the two. However, it's always a good idea to maintain your oral health, especially if you have heart problems, says Swan.

"When you have inflammation going on in your body [due to an oral disease], there are chemicals that go into the bloodstream that circulate throughout the body," he explains. Those chemicals can contribute to inflammation in other parts of the body, including your heart.

Pneumonia
Anyone age 80 or older living in a long-term care facility or retirement home increases his or her risk of contracting aspiration pneumonia if he or she practises bad oral hygiene.

"You can get a buildup of dental plaque or biofilm," says Swan. "There are many oral bacteria in the mouth of a perfectly healthy person, but for the elderly, they can breathe dental plaque or biofilm down into their lungs with bacteria. Those bacteria can cause pneumonia, which can be very serious for an 80- or 90-year-old."

If an elderly person uses a mechanical ventilator there is also a small chance that bacteria may migrate down the tube and into his or her lungs if he or she has poor oral hygiene habits.

Tooth decay
If left untreated, serious cases of tooth decay can spread and affect other parts of your body, including your eyes and brain.

"Untreated tooth decay can turn into an abscess, then swells and can compromise your ability to breathe or to swallow," warns Swan. "In its worst-case scenario, untreated tooth decay can be life-threatening."