Yes, Your Teeth Shift When You Get Older
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At my last dental cleaning, I mentioned to my hygienist that I’d recently noticed that my two bottom front teeth had started to overlap. “Oh yes, that happens to lots of people as they get older,” she said. At 42, I’ve come to peace with my perpetually achy lower back and deepening frown lines. Now this, too?
Aging is indeed likely to blame for my slightly snaggle-toothed smile, according to Kendall Park, New Jersey-based orthodontist Richard D’Avanzo, DMD. 
“When you age, you get grey, wrinkles, and your teeth shift,” Dr. D’Avanzo tells Word of Mouth. The change happens gradually, but most people start to notice it in their 30s and 40s. “When everything else starts to go,” jokes Dr. D’Avanzo.
Even people who had orthodontic intervention when they were younger notice their teeth shifting with age. “As soon as braces are removed or you stop wearing a retainer, the teeth start to move again,” says Dr. D’Avanzo.
Still, you’re not doomed to have a grin that becomes more crooked with every candle you add to your birthday cake. Shifting teeth may be normal, but they’re also fixable. The first step? Understanding the migration in your mouth.
Why do teeth shift with age?
“The mouth is a biological system where bones and ligaments constantly move and break down. It’s never static,” Dr. D’Avanzo says. Over time, as we age, our teeth, especially the ones on the bottom, have a tendency to move towards the front of the mouth. The migration causes crowding, which can become an aesthetic problem—and a functional one. “When teeth are bunched up, it’s harder to floss between them, leaving them more prone to plaque buildup,” Dr. D’Avanzo notes.
What causes your teeth to start making this slow forward march? The support structures that once kept them in place—the ligaments, muscles, bones, and tissue in and around the mouth—weaken. Jaw bones, like any other bone, become less dense with age  as it loses minerality.  That bone weakness can lead to tooth loss and shifting, says Dr. Sandra Moldovan, MS, DDS, a Beverly Hills-based periodontist and nutritionist.  Inflammation and periodontal disease  can further weaken the bone, as can a diet that’s low in vitamin D, says Dr. Moldovan.
The ligaments that anchor our teeth to the jawbone weaken, too. Periodontal ligaments are made up of connective tissue and strong collagen fibers that help teeth withstand the pressure of chewing, according to the American Dental Association.  As they start to break down, they struggle to hold the tooth in place, says Dr. Moldovan.
Our gums also become less robust and can start to recede with age, says Jeffrey Ebersole, PhD, a professor of biomedical sciences and associate dean for research at the University of Las Vegas School of Dental Medicine.  Chronic inflammation linked to poor oral care habits can make gum recession worse (as can brushing too hard), says Dr. Ebersole.
Muscles in our lips and tongue also exert force on our teeth, helping to keep them in place, but—you guessed it—they also lose their oomph with aging, especially if they aren’t regularly exercised. “Not chewing enough fiber-rich foods like fresh fruits and vegetables can cause the jaws and muscles to weaken,” says Dr. Moldovan.
General wear and tear can also cause shifting. “Teeth have contact points between them,” explains Dr. D’Avanzo. “Years of pressing and scraping against each other can create space for other teeth to shift into.” In fact, any force on a tooth can move it, says Dr. D’Avanzo. That’s why he often sees tooth shifting among nail biters and teeth grinders. Bruxism, the technical term for tooth grinding, typically happens in sleep, so you could have the habit and not realize it.
What else can cause shifting teeth in adults?
Writer Gretchen Voss doesn’t bite her nails or grind her teeth. But she did do something in her 30s that her orthodontist suspects caused the gap to open up between her top two front teeth: She had kids. “My orthodontist told me that my teeth moving was probably the result of hormones from pregnancy,” says Gretchen. “Stretch marks, deflated boobs, and crooked teeth. I mean, seriously?”
Seriously. Hormonal shifts during pregnancy can increase blood flow to the gums, making them more sensitive and raising the risk of inflammation, according to the American Pregnancy Association.  That inflammation can cause a break down of those bones and ligaments which hold teeth in place, says Dr. D’Avanzo. It can even cause tooth loss and chronic diseases, such as diabetes and cardiovascular disease. 
Relaxin, a chemical that softens joints and ligaments during pregnancy  could also be a factor. During childbirth, the hormone helps the muscles of the cervix and birth canal  soften in preparation for delivery. But it can also soften periodontal ligaments, making teeth more susceptible to shifting. (For more on the connection between pregnancy and dental health, click here.)
What can be done to straighten my teeth?
Gretchen got braces a decade ago, when she was 37. And though she says she felt out of place among the teenagers in her orthodontist’s waiting room, she’s far from alone. As of 2016, there were nearly 1.7 million adults being treated by U.S. and Canadian members of the American Association of Orthodontists.  Those stats don’t surprise Dr. D’Avanzo, who says he’s seen a big uptick in the number of adult patients in the past few years. He estimates about 40 percent of his patients are adults.
Some adults looking for a straighter smile opt for fixed braces. Brackets are temporarily stuck to teeth and joined with a wire  which exerts just enough pressure to slowly move the teeth. The wires are adjusted about every eight weeks, says Dr. D’Avanzo.
But most of D’Avanzo’s patients choose clear aligners. For this treatment, a dental scan is used to create a series of plastic aligners that are worn day and night (except when eating, brushing, or flossing). The aligners move your teeth about a quarter of a millimeter at a time, and each is worn for anywhere from 5 days to two weeks, says Dr. D’Avanzo. Clear aligners can adjust shifty teeth up to 67 percent faster than braces, according to a study from Baylor College of Dentistry,  although the study authors stress that this is only the case if people wear the aligners as instructed by their orthodontist. Minor crowding can be treated in 3-6 months with clear aligners, while more severe shifting might need up to 18 months to correct, says Dr. D’Avanzo.
Regardless of which treatment you choose, you should continue to wear a retainer at night to prevent teeth from starting to shift again.  It’s a lesson Amanda Bailey, a 35-year old designer in Wyomissing, Pennsylvania, learned first hand.
“I had braces when I was 14, and although I had a permanent retainer on my bottom teeth, I hadn’t been good about wearing my upper retainer,” she says. So when she was 30, she had invisible aligners for 13 months—and is trying to be better about wearing her retainers. “It’s amazing how quickly my teeth shifted,” she says.