The canted plane revisited: One thing you MUST check

Dr. Halligan
Dr. Halligan

The frontal occlusal plane is one of the easiest things to check. Just place a tongue depressor in the mouth, widthwise, in the premolar area and take a look.


Figure 1.


Figure 2.

That flat reference should be level with the eyes, ears, and floor. It would be unusual to see perfect alignment here, but if the tongue depressor is obviously slanted as you see in figures 1 and 2, then something is wrong.

Published research says that 76% of the time an obvious cant to the frontal occlusal plane indicates a TMJ problem, specifically an anteriorly displaced articular disc, or even absence of the disc in severe cases.

Now, I must admit that even though I have read the research, I cannot tell you the exact methodology, that is how did researchers come up with that 76% figure? It seems that it would require MRI of all the research subjects who showed a slanted occlusal plane when viewed from the front. But it does not appear that was done. I believe the stats were based on TMJ signs and symptoms.

Regardless, the canted frontal occlusal plane indicates that development of the facial bones, in particular the mandible and maxilla, did not follow the expected symmetry. And research indicates that it starts with the mandible. All long bones in the body have growth centers, each called the epiphysis. If the epiphysis is damaged or disrupted, then the growth of that bone slows or stops. The mandible has two such growth centers on the superior surface of the condyles. A partial or total disc displacement can disrupt the growth center. Since the mandible has two such growth centers, the growth is often disrupted on just one side.

Researchers have concluded that a canted frontal occlusal plane usually means that there was a childhood injury to the mandible, a fall on the chin being most common, or a blow to the side of the head. Any such blow prior to the growth spurt at around age 15 could be the cause.


Figure 3. True pan.

Figure 3 is an x-ray, in this case a ‘true pan’, from a CT scan not a simple panoramic x-ray, showing the mandible of a patient with canted occlusal plane—and plenty of TMJ symptoms to go with it. What should be obvious is the shorter left ramus of the mandible. For this person, the right side of the lower jaw developed normally in her teen years while the left side did not. The upper jaw then developed to accommodate the lower jaw.

Typically, this is the person who tells you, “Oh, my jaw has clicked like this for years.” She’ll then proceed to tell you whether or not there are symptoms of pain and dysfunction. But if a canted frontal occlusal plane is one of the leading indicators of TMJ pathology, you know that more investigation, perhaps CT scans of the jaw are needed.

Let’s assume for a moment that your patient has a canted occlusal plane. You know there is a 76% chance of a temporomandibular joint problem. But what about the other 24%? What if your patient has no joint pain, no limitation of function, and even normal joint images. All clear, right?

Well, based on the experience of dentists who read this website, I would still encourage caution. The stories I hear remind me of the children’s fairy tale, ‘The Princess and the Pea,’ because the patients I’m told about are exquisitely sensitive to tiny changes. This is speculation I suppose but I’ve heard this story often enough that if your patient has a noticeable cant, but does not appear to have a joint problem, something as simple as a small composite restoration can “cause all heck to break loose” as one person told me.

The Princess who could feel a pea through eight mattresses may have been just the girl the Prince was looking for, but she can make life in the dental office just a might stressful. The tiniest high spot on a filling will be more than noticeable to her.

Is there any research to back this up? None that I know of but keep this in mind: When you see the obviously canted occlusal plane, there is something going on that could make life difficult for restorative dentistry or orthodontics.

When I discussed this situation with Dr. Michael Miroue, an orthodontist in the San Diego area, he had this input: “What transpires is the mandible is the primary driver of the occlusal plane cant. The maxilla secondarily adapts to the canted mandible and via sutural growth become canted also. The mandibular position thus becomes the template for the maxilla. If the cant is mild, ortho can treat it via TADS (mini screws or implants). If the cant is more severe, surgery is indicated.”

For a more detailed look at how orthodontics can correct a canted occlusal plane. Please click here to see a 1MB PDF attachment.

Future research may discover why the Princess is so sensitive. It’s not her (or his) fault and it likely isn’t psychological either. That research may also lead us to treatment options not yet thought of. Meanwhile take your time and be very cautious with these folks. And remember one of Omer Reed’s famous maxims: sometimes the best dentistry is no dentistry.


Leave a Comment