How Often You Should Replace Your Toothbrush (and What Happens When You Don’t)

When it comes to cleaning there are a few rules you follow. Dust twice a week, change your bedsheets biweekly, and throw out old makeup. But what about your toothbrush?

You may prolong replacing your frayed toothbrush to get a few more uses, but it’s best to do it sooner rather than later. The truth is toothbrushes don’t last forever and not updating them could spell trouble, namely tooth decay and periodontal (gum) disease, both of which are preventable with good at-home care and regular check-ups, says Sally Cram, DDS, a spokesperson for the American Dental Association (ADA) and a practicing periodontist in Washington, DC. “We want to have the right tools, make sure they’re in the right condition and know how to use them,” she adds.

Here’s what you need to know about replacing your toothbrush and what can happen if you don’t.

How often you should replace your toothbrush

The ADA recommends replacing your brush (manual or electric) every three to four months, more often if the bristles are obviously in bad shape. You can tell if the brush is past its shelf life by looking physically at the bristles, says Dr. Cram. “You’ll notice that the tips of the bristles are starting to fray,” she says. Or the strands of the bristles may even start to unweave.

Some electric models have a blue color in between the bristles—when the blue vanishes, you’re supposed to replace the brush. Ignore this says Dr. Cram. “The acid in your saliva makes the blue disappear,” she explains. “If you don’t have a lot of acid in your saliva you may have blue bristles that still look like they’ve been scouring the tub.”

With a powered toothbrush, you only need to replace the head at regular intervals, not the entire device. (Here are the best electric toothbrushes, according to dentists.)

Exceptions to the rule

When it comes to how often you should replace your toothbrush, there are exceptions for people with a lot of crowns and fillings. “Those toothbrushes are going to get beat up and worn out a lot faster than someone who doesn’t,” says Dr. Cram. Both fillings and crowns can create a lot of uneven surfaces and rough edges in your mouth which overwork brushes.

Another exception is if you’ve been sick with something potentially contagious. If you don’t invest in a new brush after this type of illness, says Janna Burnett, DDS, clinical assistant professor of comprehensive dentistry at Texas A&M College of Dentistry in Dallas, “You could reinfect yourself.” You might also seriously consider retiring your toothbrush if you drop it on the toilet-brush cleaner or in any other unsavory location, adds Dr. Burnett.

Possibility of gum disease

“When those bristles are splayed and bent, they’re not being effective at getting down that little collar of gum tissue,” explains Dr. Cram. We need to brush and floss away plaque and bacteria from your mouth at least every 24 hours. “Just 48 hours is enough to cause inflammation which can lead to periodontal [gum] disease,” she cautions.

Signs of early gum disease (gingivitis) include but are not limited to red, swollen gums or tender and bleeding gums, and bad breath, according to the National Institute of Dental and Craniofacial Research. (Read up on early signs of gum disease you may be ignoring.) If you don’t take care of gum disease in its earliest stages, it can damage as far down to your bones, which means you can start losing your teeth.

The bacteria that cause periodontitis can affect other parts of your body as well if they get into your bloodstream. According to the American Academy of Periodontology, gum disease may be implicated in heart disease, respiratory disease, rheumatoid arthritis, and make it difficult to control blood sugar. (Here are 7 signs of disease your teeth can reveal.)

Possibility of tooth decay

Bacteria and leftover food can combine together to form plaque on teeth, which is a sticky, bacteria-containing biofilm. This plaque then feeds off sugar and starch from the food you eat to produce acids which, in turn, can erode the outer enamel layer of your teeth and lead to cavities and even tooth loss.

Fluoride in toothpaste along with water work with calcium and phosphate in your saliva to repair the enamel, explains the National Institute of Dental and Craniofacial Research. But this natural mechanism will soon be overwhelmed if you stick to a sugary, starchy diet, don’t brush your teeth, and don’t replace your toothbrush regularly.

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Buying a toothbrush

Most experts, including the ADA, recommend buying soft toothbrushes. “Hard toothbrushes have hard, stiff bristles that don’t flex and don’t bend and don’t sweep down under your gum,” says Dr. Cram. “Soft bristles do a much better job of getting into more nooks and crannies.” And that’s the only way you’re going to flush your mouth of lurking bacteria, which can cause so many problems. (Here’s what you need to know about charcoal toothbrushes.)

Also, look for brushes that have lots of bristles as opposed to sparse ones. “It’s better to have lots of bristles, then as you’re making a circular motion with the brush, you’re actually getting the little bristles to sweet under the gum tissue,” advises Dr. Cram.

The size of the head matters as well. “I get people who have really tiny mouths but are using a full-size brush,” says Dr. Cram. “They may need a toothbrush that has a more compact head. I have some adults who use children’s toothbrushes.” (This is the toothbrushing mistake everyone makes.)

The best brushing technique

The ADA recommends keeping the brush at a 45-degree angle to your gums then moving it back and forth in short strokes. Make sure to cover the outer surfaces of your teeth, the inner surfaces as well as the top (chewing) surfaces. Getting the inner surfaces of your front teeth can be tricky. The ADA also suggests doing up-and-down strokes with your brush slanted vertically.

“Ultimately you want to make sure you are focusing on the gum line,” says Dr. Burnett. “Many people just brush the eating surface.”

Your toothpaste should always contain fluoride, which protects against cavities. Practice brushing for two minutes twice a day, flossing between your teeth once a day, and get regular check-ups with a dentist. (Learn more about right and wrong brushing techniques.)

How to take care of your brush

Take good care of your toothbrush during its life span, however brief. You should rinse with tap water after each use, according to the ADA. There’s generally no reason to disinfect it and that hasn’t proven effective anyway, says the Centers for Disease Control and Prevention. In between uses, stand the brush upright—away from other toothbrushes—in the open air. Covering them up or putting them in a container can actually encourage bacteria growth.

The ADA also says not to share your toothbrush as you could end up with someone else’s germs (yes, sharing really is that bad). In three or four months—or sooner if there’s visible wear and tear—it’s time to welcome a new one into your life.