In this clinical lecture, the presenter explains mandibular entrapment as a major cause of temporomandibular joint (TMJ) pain. He begins by describing a common presentation—crowded lower incisors in a Class I occlusion with no upper arch crowding—and walks through the orthodontic sequence that creates a space discrepancy between the arches after aligning the lower incisors. The resulting residual space in the maxillary arch forces distal retraction of the upper incisors, which in turn pushes the mandibular condyle posteriorly (distalization) into the fossa, a condition he defines as mandibular entrapment. He cites literature linking upper bicuspid extractions and incisal retraction to posterior condylar positioning. The talk then presents several patient cases: a woman with an extracted upper bicuspid, migraines, and severe clenching whose pain resolved after creating intentional space distal to the upper cuspids, using removable appliances, braces, and over‑contouring of adjacent teeth; and another case where intentional residual space was left to avoid entrapment. Across the examples, he emphasizes that mandibular entrapment is common, often overlooked, and can be prevented or reversed by managing arch space, avoiding excessive retraction, and using appropriate orthodontic mechanics. The lecture ends with a call for greater awareness of this condition among clinicians.
Chapters
Welcome back. This segment is entitled, What is Mandibular Entrapment? Mandibular entrapment can be defined as basically the biggest reason that you have lots of TMJ pain patients in your practice. And let's look at and see how this happens. Many patients present for treatment with crowded lower incisors in a Class I occlusion like this. They have no crowding in the upper arch, but moderate to severe crowding in the lower arch. I was taught to remove 4 bicuspid teeth in cases like this, but I don't do that anymore. Let's explore what happens when you do that. Here then is the lower arch, and you see what happens to the lower arch as the lower incisors are aligned. After the alignment is complete, you see that there's some space remaining. Usually 2 to 3 millimeters of space remains. In the maxillary arch, however, There's still a full space left because there was no crowding to begin with, and no retraction has occurred. So, you still have a 7 to 8 millimeter space there. If you look at this from the side, you see a 2, 3, or maybe 4 millimeter space in the lower, but an 8 millimeter space in the upper, which needs to be closed. So, you close the spaces in both arches, and now you see here in this depiction, there's no space in the lower arch, and yet there's 4 or 5 millimeters of space still left in the maxillary arch. But if you look over to the left-hand side, you see that the incisors are in contact. So, what does that mean if there's no overjet and you continue to retract in the maxillary arch? What is going to happen? Pretty easy to understand this drawing when you see the bulldozer pushing back on the upper incisors and realize there's no place to go. And the other area— arrow points to the distal of the condyle. And everyone knows the anatomy in this region and knows that distalizing the condyle is not a good thing. This is essentially what mandibular entrapment is about. Now, here's an article from the refereed literature talking about this happening in upper bicuspid extraction cases. And it says that posterior positioning of the condyle after orthodontic extraction and incisal retraction may occur, but its clinical significance requires further assessment in future studies. To be honest with you, I spend many hours every day of my practice dealing with people who have mandibular entrapment and trying to reverse this. It's a big deal. Here you see it on an x-ray. You can see that the condyles are distalized in the fossa. This is not good. So, let's illustrate what do we do in a case like this. Here's a woman who's had one upper bicuspid extracted in her case, and she presents She has a skeletal asymmetry here, but her big problem is that she has migraines, which cause her to lose time away from work several times a month. Her temporomandibular joints and all the muscles of her face are tender to palpation, and she admits to a severe clenching pattern. I won't go into a long treatment here, but just say that after we've opened some spaces distal to her upper cuspids, you see about 2 millimeters of space between each upper cuspid and bicuspid on both sides. Her pain pattern seems to go away. In a matter of about 4 months, she's completely pain-free. We transitioned her into braces. This was all done, by the way, with removable appliances. We transitioned her into braces and did a more— better fine-tuning situation here, which left her with this final result, with just that amount of space. That space was dealt with by bonding and overcontouring the 2 adjacent teeth, the cuspids and first bicuspids. And she's gone from missing work several days a month to running half marathons and being pain-free, being completely cured of her mandibular entrapment problem. So, there are many ways for mandibular entrapment to occur. One is with 4 bicuspid extraction or upper bicuspid extraction. There are other ways too. I show the next case here as a case that I finished with perfect interdigitation of the posterior teeth. And I left space distal to both cuspids purposely in her case because there was no overjet. Now, she doesn't mind the space there, and if indeed she didn't like it, she could certainly have those over-contoured. But I illustrate this to show you that if I had closed those spaces up completely, as would be required for the orthodontic protocols for American Board certification, I'm almost certain she would have had mandibular entrapment, which would have probably carried with it a rather substantial pattern of symptoms. So, what is mandibular entrapment? It's something that occurs all the time. And why aren't more people aware of mandibular entrapment? That's the real question.
