Why Did My Dental Work Fail When the X-Rays Looked Fine?

Why Even the BEST Dental Diagnostics Can't Predict Every Outcome

Have you ever had a dentist tell you that everything looked perfectly fine, only to have that same tooth start hurting a few months later? Or maybe you had a crown placed on a tooth that seemed perfectly healthy, and suddenly it needed additional treatment that nobody expected. And naturally, you're wondering what the heck happened.

• Did the dentist miss something?

• Was the wrong test performed?

• Should you have had a CBCT instead of a regular X-ray?

• Did somebody make a mistake?

• Did someone "drill too far"? (That's the accusation I hear the most from people who tell me their cavity turned into a root canal at their last dentist).

Those are perfectly reasonable questions, and I've been on the receiving end of some of them more times than I can count over the past three decades of practicing dentistry. 

I LOVE diagnostic technology. I love being able to show my patients what's happening inside their mouths, and I probably take more clinical photographs than most people think any dentist could possibly need. I think pictures are worth a thousand words, and dentistry is such a visual profession that photographs make an enormous difference in helping people understand what we're seeing.

But I wish all people understood this about even the most sophisticated diagnostic equipment we have available today.  The ability to identify a problem doesn't automatically give us the ability to predict exactly what's going to happen to that tooth in the future.  And there's some pretty fascinating science explaining why. And because you know I'm a science girl, here we go on another scientific adventure...

Dentistry Has Come a LONG Way, but We Still Can't See Everything

When I graduated from dental school, our diagnostic technology looked pretty different from what we have today.  We relied on conventional X-rays, clinical exams, magnification, instruments, patient symptoms, and whatever additional information we could gather from the teeth and surrounding tissues.

We were on the edge of digital X-rays at that time, because when I started my practice just two years after I graduated, I bought my first digital X-ray system, and I was CUTTING EDGE for the day! It's really rare to see the old-school film X-rays now, thank goodness. I was especially excited about digital imaging because my system substantially reduced radiation exposure compared with the older film technology we were using.

Nowadays, we also have digital CBCT imaging, intraoral cameras, scanners, advanced diagnostic devices, and increasingly sophisticated software to help us interpret what we're seeing.  It's pretty amazing how much dentistry has changed in thirty-two years!  A CBCT scan allows us to examine three-dimensional anatomy in ways that simply weren't possible with conventional dental X-rays. We can evaluate bone structures, root anatomy, certain fractures, impacted teeth, and areas of suspected infection with incredible detail.  But even with all of that technology, there are still things we can't see. And sometimes those are the things that end up causing the biggest problems.

An X-Ray Is a Picture of What's Happening, Not a Prediction of What Happens Next

Let's talk about regular dental X-rays for a minute.  When we take an X-ray, we're looking at how different structures absorb radiation. Enamel, dentin, bone, fillings, and other materials show up differently, which helps us identify problems that might otherwise go unnoticed.  We can find cavities between teeth, look for bone loss, evaluate the roots, and identify signs of certain infections.  But a regular dental X-ray is still a 2 dimensional picture of something that's three-dimensional.

Imagine trying to figure out everything that's happening inside your house by looking at a photograph of the outside.  You might notice that the roof looks great and the windows are intact, but that photograph isn't going to tell you whether a pipe is leaking behind the kitchen cabinets or termites are having a party inside the walls.  Teeth can be a little like that.  A large filling may look perfectly fine on an X-ray while cracks are developing underneath it. A cavity may be much deeper than it appears. And a tooth may have inflammation inside it long before that inflammation creates something visible on an X-ray.

There's research showing just how much our ability to find cavities depends on HOW we're looking for them.  In 2021, researchers compared several ways dentists look for cavities between teeth, including regular dental X-rays, visual exams, and newer technologies that use light. They found that the different methods had different strengths, and that how well a test worked depended partly on how far the decay had progressed. [1]. I think that makes perfect sense.

There are things I can see with my eyes that don't necessarily show up clearly on an X-ray. And there are things I can see on an X-ray that I couldn't possibly identify by looking at the outside of the tooth.  That's why I use multiple tools when I'm trying to understand what's happening.  And even then, I know there may be more going on than I can see.

CBCT Scans Are AMAZING, but They Aren't Magic

I remember when three-dimensional dental imaging started becoming more widely available, and I was absolutely fascinated by what we could see.  I think when I bought my CBCT machine maybe 1% of dentists had them.  I think the number is sitting at about 10% of dentists now, just 10 years later.  That's a huge leap, but it's not 100%... YET.  Because those machines are a HUGE investment.  

Instead of looking at a flat image, we could examine the jaws and teeth from different directions, move through layers of bone, and identify problems that conventional X-rays sometimes missed.  For someone who's spent her career trying to understand what's happening beneath the surface, that technology was a BIG deal.  And the science confirms that it can change how dentists diagnose and treat problems.

In 2022, researchers looked at sixteen studies investigating whether CBCT scans changed dentists' treatment recommendations for teeth with root canal problems.  In fifteen of those studies, the additional imaging caused dentists to change at least some of their treatment plans. In several studies, approximately one-quarter to two-thirds of the recommendations changed after the dentists reviewed the three-dimensional images. [2]. That's a HUGE difference!

Imagine being told that a tooth needs one type of treatment, then having another scan that reveals additional information and completely changes the recommendation.  The first dentist may have made a perfectly reasonable decision based on the information available at the time.  And the second dentist may now have information that wasn't visible before.  You need to know that even a CBCT can miss important problems.

In 2021, researchers examined how well CBCT scans could find vertical root fractures in teeth that had already received root canal treatment.  These are cracks that run along the root, and they're particularly important because they can make a tooth impossible to save.  The researchers found that CBCT identified approximately 78% of the confirmed fractures. [3]. That means roughly 22% of those fractures were missed, even with three-dimensional imaging.  Now THAT should get your attention!

Another large review published in 2025 looked at 100 studies and found that the ability to identify these fractures depended on several things, including how large the crack was, whether it extended completely through the root, and whether materials inside the tooth interfered with the image. [4]. And that's one of the reasons I think patients need to understand that a normal-looking scan doesn't always mean the tooth is perfectly healthy.  Sometimes there really IS a problem, but it's too small or too hidden for our current technology to identify.

Sometimes the Dentist Doesn't Find the Problem Until the Filling Comes Out

I can't tell you how many times I've had this happen over the years.  A patient comes in with a large old filling. Maybe it's been there for twenty years. Maybe it's starting to break down, or there's some new decay around the edges.  Maybe the tooth is showing cracks on the marginal ridges of the teeth.  The tooth might not hurt at all.  We take X-rays, do our exam, and determine that the filling needs to be replaced.  Then I remove the old filling.  And SURPRISE!  There's a crack running across the floor of the preparation that nobody could see before the filling was removed.

Sometimes it's relatively minor. Other times it's a BIG crack, and suddenly we're having a very different conversation about whether the tooth needs a crown or can even be saved.  I see this often enough that it's one of the things I try to explain before removing large restorations.  I may be planning to place another filling, but I can't promise that's what the tooth will need once we can actually see what's underneath the old one.

This is particularly important when we're dealing with teeth that have been exposed to years of grinding, clenching, or uneven chewing forces.  A tooth can accumulate microscopic damage over a very long period of time without announcing that something is wrong.  Eventually, one more bite may be enough to make the crack spread or the tooth fracture.  The patient thinks the tooth suddenly broke, but the underlying damage may have been developing for years.  That's why I spend so much time talking about structural support and the forces teeth have to tolerate.  A tooth that's already weakened doesn't magically become strong again because we put a beautiful new filling in it.

"But My Tooth Didn't Hurt Until the Dentist Drilled on It!"

Oh, if I had a dollar for every time I've heard this one!  And I completely understand why people think that way.  If your tooth felt fine before the appointment and started hurting afterward, it's perfectly logical to wonder whether the dentist caused the problem.  Sometimes the treatment really did irritate the tooth. Drilling creates heat and vibration, dental materials can affect the tissues, and removing decay may leave very little healthy tooth structure between the new filling and the nerve.  So yes, dental treatment itself can contribute to a tooth becoming sensitive or painful.

But there's another part of the story that people usually don't know about.  A tooth can be seriously inflamed inside without hurting.  The pulp, which is the living tissue inside the tooth, contains blood vessels, nerves, immune cells, and other tissues that help keep the tooth alive.  When decay gets deep enough, bacteria and the substances they produce can irritate that tissue long before the patient develops symptoms.  And because the pulp is enclosed inside hard tooth structure, inflammation can become particularly complicated.

Sometimes the tissue can recover after the decay is removed and the tooth is properly restored.  Sometimes it can't.  And sometimes we can't determine exactly how damaged the pulp already was until the tooth begins responding to treatment.  This is why I believe preserving living teeth is SO important. Once the pulp dies or is removed during a root canal, we've permanently lost the living tissue that originally occupied that space.  I want to protect that tissue whenever reasonably possible.

But I also want people to understand that even when we do everything we can to preserve it, healing isn't guaranteed.  And the fact that a tooth develops pain after treatment doesn't automatically tell us whether the damage came from the procedure, the original cavity, a hidden crack, or some combination of factors.  That's what we have to investigate.

Even Testing the Nerve Doesn't Tell Us Everything

When a patient comes in with a painful tooth, we have several ways to try to figure out what's happening inside it.  We might put something cold on the tooth, use an electrical tester, tap on it, have the patient bite on something, or check the tissues around the roots.  And each of those tests tells us something different.

But most people don't know, for example, that when we use cold or electricity to test a tooth, we're primarily checking whether the nerves respond.  We're not actually measuring how healthy the blood supply is or how much inflammation is inside the tooth.  Those are different things.  In 2018, researchers reviewed 28 studies comparing five different ways of testing whether teeth were alive.  They found that cold testing correctly identified approximately 87% of living pulps, while electrical testing correctly identified approximately 72%. [5]. So even our commonly used nerve tests can give us incomplete information.

The researchers also found that technologies designed to evaluate blood flow or oxygen levels within the tooth performed better in the studies they reviewed.  And I find that FASCINATING.  There's a big biological difference between asking whether a nerve can respond to something cold and asking whether the tissue is actually receiving the blood and oxygen it needs to survive.  I would LOVE to have technology that could tell me exactly how inflamed a pulp is, how much healthy tissue remains, and what the chances are that the tooth will recover after treatment.  Wouldn't THAT make our jobs easier?

But we don't have a little window into every tooth that lets us watch what's happening at the cellular level.  YET.  I think at some point technology is going to figure it out!  But in the meantime, we use the best information we can gather, compare the different findings, and make our best judgment about what the tooth is likely to tolerate.  Sometimes we get it right.  And sometimes a tooth that looked promising surprises everybody.

We Can See Teeth, but We Can't See Every Force They're Living With

The forces that teeth experience are things that we have underestimated in dentistry.  An X-ray can show me a filling, a root, or the bone supporting a tooth. But it doesn't tell me exactly how hard someone clenches their jaw while they're asleep.  It doesn't tell me how many times their chewing muscles activate overnight, or whether their bite is putting excessive pressure on one particular tooth.  And it definitely doesn't tell me whether their breathing during sleep is contributing to those muscle activities.  This is especially important in patients who grind their teeth.

As an airway-centered biological dentist, I pay VERY close attention to grinding, clenching, and unusual tooth wear.  I've told y'all before that when I screen patients with these findings for sleep-disordered breathing, an extraordinarily high percentage of the patients I've tested are diagnosed with some form of sleep-disordered breathing by our board-certified sleep medicine specialists.  And the research supports why that relationship deserves attention.

In 2014, researchers found that patients with obstructive sleep apnea had nearly FOUR TIMES the odds of experiencing sleep bruxism compared with people without sleep apnea. [6]. And in 2022, when researchers treated patients' obstructive sleep apnea using either CPAP or a mandibular advancement device, the patients experienced significant reductions in their grinding activity. [7]. In other words, they treated the breathing problem, and the grinding improved in many of those patients.  That's pretty compelling evidence that the two conditions are connected in at least some people.  And it also demonstrates why I'm not satisfied with simply repairing the damage from grinding without investigating WHY the grinding is happening.

Now think about what this means for a patient who's repeatedly breaking crowns or fillings.  The dentist may be using excellent materials and doing beautiful work, but if we haven't identified the forces contributing to the repeated failures, we may keep repairing the same problems.  And that gets expensive, frustrating, and downright exhausting for everyone involved.

Sometimes the Pain Isn't Even Coming From the Tooth

Let's talk about one of the most frustrating situations in dentistry.  Mystery pain.  I don't know a single dentist who's practiced for any length of time without encountering patients who are experiencing very real pain that we simply can't identify or explain with the usual tests.  The patient may be absolutely convinced that a particular tooth is hurting.  Or worse, they can't identify the tooth that's hurting.  I promise, we aren't mind readers!    We examine it, take X-rays, test the nerve, check the bite, and look for cracks or other obvious problems.  And everything looks pretty normal.  The patient is still hurting.

Now what?  Sometimes there's a dental problem that we haven't been able to identify yet.  But sometimes the pain is actually coming from somewhere else.  One tooth can refer pain further on down the line. Or UP the line. The muscles around the jaw can refer pain into the teeth. Problems involving certain nerves can create sensations that feel like toothaches. And some people develop ongoing pain even after the original dental problem has been treated. 

I had a patient a few years ago who had been to several endodontists, had root canals on his upper right first and second molars and could not make the pain in those teeth go away. He was so frustrated.  So he ended up in my chair.  I did what I always do - I took a CBCT.  It turned out this gentleman had a severe infection on his lower right first permanent molar.  It was LARGE.  But he didn't have any pain on the bottom.  His pain was on the top.  So I suggested to him we numb the bottom tooth and see if the top tooth pain went away.  Within a few minutes, his upper tooth pain resolved.  THAT is what referred pain can look like.  

There's research discussing exactly this problem.  A 2024 article examined why some patients continue experiencing toothaches even after receiving multiple dental treatments. The authors explained that pain originating outside the tooth can be mistaken for a dental problem, sometimes leading to procedures that don't actually resolve the symptoms. [8]. That's incredibly important.

I don't want to remove a tooth simply because someone points to it and says it hurts, especially when the clinical findings don't explain WHY it hurts.  I have no interest in doing unnecessary surgery!  The patient who had the tooth pain on the top might have been able to avoid root canals on 2 molars had the dentists before he saw me taken a bigger picture kind of look - one dentist and two endodontists only took images of the upper right molars.  NONE of them did a CBCT of the entire area, upper and lower teeth, to see if there was something else causing the pain.  Until we did.  And surprise, surprise, there was a lower molar referring pain to the upper 2 molars.  Months of pain could have been avoided as well as two unnecessary root canals.  

We need to understand what we're treating.  Sometimes it means looking at bigger imaging.  And sometimes that means involving other healthcare professionals, including orofacial pain specialists, neurologists, physicians, or other clinicians who can help us investigate the problem.  I think one of the most important things we can tell someone with unexplained pain is that we believe they're hurting, even if we haven't figured out exactly what's causing it yet.  Because having a normal-looking X-ray doesn't mean somebody is imagining their symptoms.  It means we need to keep looking for an explanation.

More Testing Doesn't Automatically Mean Better Answers

I'm sure you can imagine how easy it would be for someone like me, who LOVES technology, to get carried away collecting information.  And believe me, if there were a machine that could tell me exactly what every tooth was going to do for the next fifty years, I'd probably be first in line to buy it.  But there's a difference between getting useful information and collecting information simply because we can.

A CBCT can be incredibly valuable when we're trying to understand complicated root anatomy, hidden infections, bone conditions, or certain fractures.  It gives us a snapshot in time of what a person's anatomy looks like.  But if the problem is that a patient has significant nighttime grinding, the answer may involve evaluating their sleep rather than taking another scan.  A sleep study gives us a snapshot of their sleep OVER time - how many times they stop breathing while sleeping over a minimum 4 hour period.    If the patient has a swallowing problem, we may need to evaluate oral muscle function.  And if they're experiencing unexplained pain, we may need a different kind of specialist instead of another dental image.

A 2025 review examined 26 studies investigating how CBCT imaging influenced dentists' diagnoses and treatment decisions. The researchers found that the scans often changed recommendations, especially in more complicated cases. [9]. And you would not believe how many abscessed teeth are missed with 2 dimensional xrays.  It means the technology can help us make better decisions when we use it for the right reasons.

But the real question should always be what we're trying to find out and whether the test we're ordering can actually help answer that question.  Sometimes more testing gives us exactly the information we need.  And sometimes we're asking a machine to answer a question it was never designed to answer in the first place.  But if we don't test, we don't know.  And I'm not a fan of guessing.