What's to be learned from this? You can avoid infecting yourself with bacteria, and prevent a lot of illnesses, with one simple act—changing your toothbrush at least every three months.

Most of us have heard this before. But a survey conducted by Colgate-Palmolive showed that only 8.6 percent of us actually do it.

"A toothbrush is less expensive than a Big Mac, but some of us are so cheap that we just can't find the money to buy a new brush," said Tom Glass, D.D.S., Ph.D., University of Oklahoma College of Dentistry and Medicine oral pathology department chair person.

Glass recommends replacing your toothbrush even more frequently than every three months. "Healthy people should buy a new toothbrush every two weeks. People with gum problems, other oral disease, or weakened immune systems should change brushes more often," he said.

Toothbrush bristles wear down relatively quickly. Once they're frayed and bent, they can't slide under the tissues to clean under the gum line, so they don't clean your teeth as well as they should.

Besides being inefficient tooth-cleaners, old, frayed bristles hide more bacteria and other disease-causing microorganisms.

A new toothbrush costs about two dollars—less if you watch for sales and use manufacturer's coupons. If taking time to buy a new one is where you're having a problem, then buy several the next time you're at the store or buy them in bulk at a warehouse shopping club. And start changing your toothbrush at the first sign of wear. It's a low-effort, low-cost way to increase your overall health.

Sources: Chicago Dental Society
American Dental Association