Aaron: I’m sure you’ve heard this when you’re sitting in the dentist’s chair: “Would you like some bitewing x-rays?” And I mean, nobody likes the x-rays, but your dentist likely recommends them every year. They’re pretty painless, they don’t take too much time, and they won’t cost you penny if you’re covered by insurance. But do you need them? That’s the topic of this week’s Healthcare Triage.

[Healthcare Triage intro plays]

Special thanks to my colleague Austin Frakt whose Upshot column formed the basis for this episode.

The American Dental Association says that adults without apparent dental problems do not need dental x-rays of any kind every year. Adults who properly care for their teeth and have no symptoms of oral disease or cavities can go two to three years between bitewing x-rays. Adults with a high risk of cavities, like those with a history of them, should probably get them at least every 18 months and possibly more frequently, depending on the condition of their teeth and gums.

The interval between x-rays should be and is determined by the rate at which cavities develop. Typically it takes about two years or more for cavities to penetrate your adult tooth enamel. The rate is faster for kids, so the recommended bitewing intervals are shorter for them. However, children with adequately spaced primary, or baby teeth, and no cavities don't need any dental x-rays either. Older children with a low propensity for cavities can go 18 months to three years between them. Those at the highest risk may need them more often than that.

Bitewing and other dental x-rays do have their place. There is risk in not taking them. Sometimes decay can spread quickly. The x-rays help dentists to see cavities, gum disease, the position of teeth still below the gum line, and other dental conditions not visible with the naked eye. Other kinds of dental and orthodontic imaging like full mouth, full head, panographs, or 3-D cone beam computed tomography reveal more. But dentists tend to over use them.

Jay Friedman, a dentist who advises Consumer Reports on dental issues, has been warning of overuse of dental imaging since the nineteen seventies. Let's quote him: "Many patients of all ages receive bitewing x-rays far more frequently than necessary or recommended, and adults in good dental health can go a decade between full mouth x rays. Other x-rays used for orthodontic treatments, wisdom tooth extraction and implants, like cephalographs, or side view x-rays of the skull and jaws, or 3-D cone beam computed tomography aren't needed on a routine basis either, according to Dr. Freeman.

One study found that although x-ray images increase orthodontist confidence in their diagnosis and treatment plans, the vast majority of them are formed before viewing the x-rays, and all x-rays can be harmful, though the radiation dose of bitewings is relatively low. Of all the medical radiation patients receive, dental x-rays account for less than three percent, but the harm from radiation is cumulative; every x-ray adds to the risk of damage that can lead to cancer.

An unnecessary bitewing or other dental x-ray is an unnecessary harm, and a cone beam CT scan confers the same radiation dose as six traditional dental x-rays, with only limited evidence of greater diagnostic or treatment value over imaging with lower radiation. And though dental x-rays do blast a relatively low dose of radiation, one study of over 2,700 patients appeared to find a link to an increased risk of intracranial meningioma, the most common form of brain tumor. Patients with the tumor were twice as likely as patients without one to have had a bitewing x-ray, although we should note that the radiation exposure from the x-rays in this study was greater than in the current era.

Another limitation of the study is that its findings were based on patient recall of dental x-rays, not more objective medical data, which is not available. However, the study is consistent with earlier and smaller studies that document an increased risk of tumors associated with dental x-rays.

And let's be clear: though your insurance may cover annual bitewings they're not free! The prices insurers or uninsured patients pay vary, but a full set of bitewings typically runs about 60 bucks. That's as much as the price of cleaning at many dental offices. So when dentists take bitewings at routine visits they may be doubling their revenue! Other types of dental x-rays can cost more. For some people, it's a needless expense that comes with needless risk. Next time your dentist asks if you want those bitewing x-rays, you wouldn't be wrong to think hard before getting them.

Healthcare triage is supported in part by viewers like you through patreon.com, a service that allows you to support the show through a monthly donation. We'd especially like to thank our research associate Joe Sevits and our surgeon Admiral Sam. Thanks Joe! Thanks Sam! More information can be found at Patreon.com/healthcaretriage.