Can Cavities Be Detected By a Laser?

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Hi, I’m Dr. B, practicing functional dentist for 35 years. I graduated from the Dugoni School of Dentistry in San Francisco, CA in 1987 and am a member of the American Academy of Dental Sleep Medicine (AADSM), Academy of General Dentistry (Chicago, IL), American Academy for Oral Systemic Health (AAOSH), and Dental Board of California. I'm on a mission to empower people everywhere with the same evidence-based, easy-to-understand dental health advice that my patients get. Learn more about Dr. B

Q: Cavities Question: My dentist recently started using a tool that detects cavities with a laser. I’ve had only two cavities my whole life, but at my last visit, the laser tool detected four new cavities! This feels wrong to me. What do you think about this tool? Could it be overly sensitive or inaccurate?

A: Laser tools can be helpful, especially for diagnosing hidden cavities at the top of the tooth, but they should never replace a visual examination done by your dentist.

These devices work by shooting safe and painless light at a tooth. The tooth absorbs some of this light and reflects the rest of it back to the sensor, which shows a digital reading. Generally, the higher the number, the more severe the decay.

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  • Earlier detection. Decay at the tooth surface that might normally be hidden in an x-ray, and according to studies, these tools do a good job picking up this type of decay.
  • Discovering cavities an x-ray couldn’t pick up.


  • Doesn’t work on teeth with fillings.
  • Can indicate a cavity when there isn’t one. In situations where a cavity is obvious, the tool works well. But in the gray areas, the tool might be too sensitive.
  • Can’t diagnose a cavity by itself. Studies show it works well in providing the dentist additional information, but it can’t work by itself.
  • Can’t replace an x-ray. These tools are not superior to a visual exam done by your dentist, according to a 2006 study.

The device doesn’t actually say, “You have a cavity.” It’s up to your dentist to judge whether it’s a cavity or not by comparing the tool’s readings to a baseline.

Your dentist should be using this tool to provide additional information when diagnosing a cavity. The tool shouldn’t be the only data point s/he uses when diagnosing a cavity.

X-rays and these laser tools complement each other; x-rays are good at finding cavities in between teeth and on the roots. Laser tools are good at find cavities on the tooth’s biting surface.

Make sure your dentist has a philosophy that conservative dentistry is best. There is a minority of dentists out there who tend to overtreat aggressively. Trust your gut on this one; if you feel like the tool is being oversensitive, get a second opinion.

Be aware that your insurance company might be providing a financial incentive for your dentist to do a filling. Insurance plans tend to cover all fillings, whether for a micro-cavitity discovered by the laser tool or full-blown cavities discovered through x-ray.

Having used this tool before, I have seen some inconsistencies in its behavior. It works well in situations when there is plain clinical evidence that there is a cavity. In situations where there’s more of a gray area, I’ve found it doesn’t work as well, which is why I don’t use one in my practice and rely on the visual exam when diagnosing decay.

What concerns me about this tool is that it is much more sensitive. Areas of decay that the tool picks up might remineralize on their own and not turn into a cavity. Some dentists believe that it’s better to fill these areas right area before the area turns into a full-blown cavity. I like to give my patients a “wait and watch” approach because sometimes it’s hard to know whether a lesion will develop into a cavity or not.

Ask your dentist what s/he thinks about “waiting and watching” the cavities that the laser tool picked up. Ask if it’s possible that those areas of decay could remineralize on their own without needing a filling. Of course, you’ll want to be careful if you take the “waiting and watching” approach because decay can spread quickly.

The take home message: these tools can be a great source of additional information. The only thing that would concern me, if I was in your shoes, is a dentist relying on the tool too much. In my experience, these tools at best give the dentist more information, and at worst, misleading to dentists and patients.

Mark Burhenne DDS

Learn More: Reversing Tooth Decay and Healing Cavities Naturally: Top Questions Answered