Jeanie (not her real name), a young lady just 20 years old, suffered jaw pain for several years and in recent months it had become much worse. Her dentist referred her to me for a TMJ exam. I measured range of motion (38 mm maximum opening with a definite click) and then asked her to close. When I watched her bite down, it looked as though she contacted only on the left side posterior teeth with an open bite on the right side. T-scan showed 85% occlusal force on the left.
The second I saw her temporomandibular joint x-rays I was sure there had been an earlier trauma. The left ramus of the mandible was less than pencil thin and very short. The left condyle was flattened.
“Did you have a head trauma when you were about 10 years old?” I asked her.
I saw the look of surprise in her eyes, but she said, ‘Yes, I guess I was about that age. It was before I had braces. It was a pretty bad fall. Why do you ask that?”
“Well, certainly there are signs of trauma on the left side, and it looks like something that happened in childhood.”
Later, I talked with her father. “That’s right,” he said. “She was just 10. She even had stitches and I think she was knocked out for awhile.”
I talked with her orthodontist as well. He had also seen her recently and had observed how drastically her occlusion was off. He sounded defensive. “I swear, she had good occlusion when I was done with ortho. It didn’t look anything like it does now. I don’t think this is my fault.”
“Oh, I’m sure you’re right,” I told him. “Your orthodontic result was probably fine.”
She had been in braces from age 11 to 14. I was curious to see if there was unequal ramus length even then, but those older panoramic films were not available.
The orthodontist wanted to know one more thing. “How could her bite change so dramatically?”
“There was a study at the University of Texas,” I told him, “proving that childhood head trauma can damage the growth plate of the mandible—and usually on just one side. And it does not have to be a major trauma such as a fractured jaw. So imagine the ramus on the right side growing longer and longer over time. At the same time, development of the left ramus and condyle either slowed or perhaps stopped completely at the time of the trauma. The left side teeth were already in contact. But as the right side grew longer, the right side teeth began to separate. You might think that with continued eruption, the teeth would still contact normally. Apparently, eruption could not keep up with the growth of the mandible.
“So, it’s as if she’s driving a car with a tiny wheel on the left and a big wheel on the right. Everything is off. It has been six years since you finished orthodontics. There has been plenty of time for things to change, especially with growth occurring only on one side. So, I don’t think what we’re seeing is your fault at all. I think it’s safe to assume that the occlusion was acceptable when you finished.”
As I mentioned earlier, the left TM joint clicked on opening. Joint vibration analysis (JVA, Bioresearch) results were consistent with partial disc displacement on the left. Therefore, my challenge was to center what remained of the left condyle in the glenoid fossa and get the disc back onto the condyle. With the bite so dramatically far off, I also wanted to fabricate both day and nighttime appliances that would give her even occlusion on both sides.
I told the young woman and her parents that the left side of the mandible was not going to magically grow and catch up with the right. Therefore, although I might achieve improved occlusion, she was almost certainly going to have orthodontics re-treated. But with growth and development now complete, this time the result would be permanent.
Is there a take home lesson here? When there has been a significant head trauma in childhood, the likelihood of altered mandibular growth is high. Therefore, dentists and orthodontists should watch for signs of unequal ramus development along with altered occlusion. A cone beam CT scan of the TMJs would be appropriate after such an injury. Unfortunately, the TMJ is one area often overlooked when examining a child who has suffered head trauma.
One sign that is easy to spot is canted frontal occlusal plane—just place a tongue depressor from right to left across the dental arch and ask the patient to close. Is that tongue depressor level with the floor, the ears and eyes? If not, you should suspect damage to the temporomandibular joint on one side with the resultant uneven development. Bear in mind that the cant will only become apparent after unequal development of the rami.
Facial development is complete by age 20 for most females, but if there is evidence of uneven growth of the mandible, consider a TMJ exam including joint x-rays, JVA, and physical exam. For Jeanie, age 14 or 15 would not have been too soon to begin TMJ therapy.
I saw Jeanie this week. It’s her third week in treatment and her jaw pain is now gone and she opens 45 mm. We’re off to a good start, but because of the occlusal problems I’m quite sure there will be stage two treatment—doing orthodontics again.
