It’s almost impossible to prove a cause-effect relationship between dental neglect and various conditions because researchers would have to create a control group that ignored their teeth completely for a long time — something that would likely be harmful enough to be considered unethical. But there’s mounting evidence that shows an association between poor dental hygiene and a wide variety of ills.
You should visit the dentist at least once a year, and the ADA recommends that you brush twice a day for two minutes and floss once a day. If you choose to ignore their advice, you’ll get cavities, sure — but here are 13 other things you’re at risk of, some more common than others.

1. Gum disease

Most people don’t realize this, but your gums are not supposed to bleed when you brush and floss. If yours do, you probably have gum disease — or are at least well on your way. Gingivitis, the milder form of gum disease, makes gums red, swollen, and quick-to-bleed — part of a response to the bacteria in the plaque that builds up between your teeth and gums. More than half of Americans have gingivitis.

If plaque spreads, the immune response heightens and can destroy tissues and bones in the mouth, creating pockets between the teeth that can become infected. (Other conditions unrelated to oral hygiene habits can also have these effects.) At this severe stage, gum disease is called periodontitis, and it can become chronic. Google “periodontitis,” and you might become more vigilant about oral hygiene.

Source: American Academy of Periodontology; Clinical Calcium, 2012

2. Tooth loss

If you’ve never worried about losing your teeth, you should start. Adults 20 to 64 have lost an average of seven (permanent) teeth, and 10% of Americans between 50 and 64 have absolutely no teeth left. Both cavities and gum disease can end in tooth loss.

Source: National Institute of Dental and Craniofacial Research

3. Bad breath

Bad breath, clinically called halitosis, may affect as much as 65% of the population. A number of conditions can have halitosis as a symptom, but the number one by far is poor oral hygiene. Food particles that linger long after meals can start to stink, and the less you brush and floss, the more potentially malodorous bacteria build up in your mouth. The coating on your tongue is also a key contributor to bad breath, and some research has suggested that cleaning your tongue — along with regular brushing and flossing, of course — may help reign in this problem.

Source: Internal and Emergency Medicine, 2011; International Journal of Oral Science, 2012; Nursing Research, 2013

4. Dementia

A large, long-term study of residents at a Laguna Hills retirement community suggests that there may be a link between poor dental health and dementia, although it’s possible that people with better oral hygiene have better health habits in general. Researchers followed 5,468 people for 18 years and found that — among those who still had teeth — those “who reported not brushing their teeth daily had a 22% to 65% greater risk of dementia than those who brushed three times daily.” In addition, a small study found that the brains of patients with Alzheimer’s had more bacteria associated with gum disease than did those belonging to the cognitively healthy.

Source: Journal of the American Geriatrics Society, 2012; Journal of Alzheimer’s Disease, 2013

5. Pneumonia

When pathogens lurk in your mouth, you inhale them right into your lungs, where they can wreak all kinds of havoc. One major review pointed to this process as the reason for an association between poor oral hygiene and hospital-acquired pneumonia. Improving oral hygiene — through some methods beyond brushing and flossing in this case — reduced the incidence of such pneomonia by 40%. Another study of 315 patients in a Brazilian hospital found that those with periodontitis were almost three times as likely to have pneomonia.

Source: Annals of Periodontology, 2003; Journal of Periodontology, 2013; Gerondontology, 2013

6. Erectile dysfunction

A connection between dental disease and erectile dysfunction may seem remote, but preliminary research suggests that the conditions could be linked. They both have been tied to Vitamin D deficiency, smoking, and general inflammation, but the exact reason for the association is still a mystery. One study in rats found that periodontitis impaired penis function. While it’s unclear whether the same direct effects would be found in humans, in a group of patients between 30 and 40, 53% of those with erectile dysfunction had severe periodontitis, while only 23% of those without ED did. “We think that it will be of benefit to consider periodontal disease as a causative clinical condition of ED in such patients,” the authors wrote.

Source: The Journal of Sexual Medicine, 2011; The Journal of Sexual Medicine, 2012; Journal of Clinical Periodontology, 2012

7. Brain abscess

Often caused by bacterial infection, an abscess is a collection of pus, with swelling and inflammation around it. In the brain, it is fatal if left untreated. “A poor dental condition, notably destructive periodontal disease, can be a risk for life-threatening” disease in other parts of the body, noted a team of scientists who pinpointed a patient’s extremely poor dental health as the likely cause of his life-threatening brain abscess. Brain abscesses are rare, and there has been no systematic study linking them to bad dental hygiene. But the authors noted at least 12 other case reports of brain abscess that pointed to poor dental hygiene as the probable cause.

Source: Journal of Clinical Periodontology, 2011

8. Diabetes

Dentists have long known that diabetes is a risk factor for periodontitis, but now research is beginning to indicate that the relationship may be bidirectional. Extremely poor dental health may also be a risk factor for insulin resistance (often called “pre-diabetes”) and diabetes, largely because it increases inflammation. Some studies have even indicated that in patients with both conditions, reigning in periodontitis may improve diabetes control.

Source: Annals of Periodontology, 1998; Diabetes Care, 2010; Diabetes & Metabolism Journal, 2012; Journal of Applied Oral Science, 2013

9. Kidney disease

About 3.7% of U.S. adults have chronic kidney disease, but certain people are more at risk. People with periodontal disease were 4.5 times more likely to have chronic kidney disease, making poor dental health a stronger predictor for CKD than high cholesterol. Adults with no remaining teeth were also 11 times more likely to have chronic kidney disease. While dental disease is not the strongest risk factor — people older than 60 are 27 times more likely to have chronic kidney disease than younger people, for example — another study confirmed that periodontitis may be a significant risk for kidney disease, even after controlling for underlying health conditions that contribute to both.

Source: American Journal of Kidney Disease, 2008; Journal of Periodontology, 2010

10. Heart disease?

Multiple studies have suggested that there may be a connection between gum disease and heart disease, both of which are associated with inflammation. “Adding oral health self-care… is prudent to improve patients’ oral health and possibly reduces [coronary heart disease],” concluded one study. “Periodontal disease caused by pathogen bacteria… could represent one of several possible causal factors of heart disease,” concluded another.

The authors of a 2008 review for the U.S. Preventative Services Task Force recommended that periodontal disease be considered a marker of risk for heart disease, independent of traditional risk factors — even though they noted a lack of evidence demonstrating a causal relationship.

But a scientific statement from the American Heart Association in 2012 urged caution: Periodontal disease and heart disease share many underlying risk factors; there’s no reason to think that dental problems directly cause heart disease; and treating periodontitis reduces inflammation but does nothing to alter the course of heart disease, the authors concluded.

Source: Journal of General Internal Medicine, 2008; Current Opinion in Nephrology and Hypertension, 2010; General Dentistry, 2012; Circulation, 2012

11. Pregnancy complications

Gingivitis affects 60 to 75% of pregnant women, and it’s especially important that expectant mothers tend to their teeth. When pregnant women have serious dental problems, their infants are more likely to develop cavities. Poor maternal oral health is also associated with low birth weight and preterm birth, although there’s not enough evidence yet to know whether it’s an independent risk factor. Researchers suspect that one of two mechanisms may be at play: Either overall inflammation is heightened, or oral bacteria that enter the bloodstream eventually colonize the placenta, causing an inflammatory response.

Source: Journal of Clinical Nursing, 2010; Ginekologia Polska, 2012; Dental Clinics of North America, 2013

12. Ulcers

In people with periodontitis, the plaque that forms in the pockets beneath the gum line can become a reservoir for Helicobacter pylori, the bacterium that is asymptomatic in most but is responsible for stomach ulcers when it flares up. Helicobacter pylori can be transmitted orally, and large epidemiological studies have found a positive association between periodontitis and a positive test for the bacterium, which is also a risk factor for stomach cancer. Different researchers have come to somewhat different conclusions, but the bacterial pockets that form during periodontitis unquestionably pose a risk for various kinds of bacterial growth and infection.

Source: Gut, 1995; American Journal of Public Health, 2002; Clinical Microbiology Reviews, 2010

13. Cancer

“Recent evidence suggests that the extent and severity of periodontal disease and tooth loss may be associated with an increased risk of malignant disease,” concluded one researcher, after reviewing previous studies suggesting an association between poor oral health and cancer. Gum disease and dental problems are also associated with HPV, which causes up to 80 percent of oral cancers. While smoking is a major risk factor for both gum disease and cancer, a study last year of 3,439 people identified poor oral health as an independent risk factor for HPV, even when smoking habits were accounted for. Other preliminary research has suggested that periodontitis may promote the growth of cancerous cells in the mouth.