Mandibular Movements

Follow along with Dr. Mark Piper as he explains normal and abnormal mandibular movements. Video Transcript: Dr. Mark Piper : What I have here is Anomalous Medical Software showing the fully occluded tooth position, and the reason the teeth are highlighted in blue is because when they are in contact in this particular setting in the program software they're going to show up blue. When the teeth are out of contact then they're going to be white. I'm going to first demonstrate excursion with guidance to the right. As you can see the left lateral pterygoid muscle is contracting to give us right and lateral excursion of the mandible. Now I'm going to switch to left lateral excursion. And you can see that the right lateral pterygoid muscle is contracting to go into a left lateral as we do so the posterior teeth are separating on the right side. Contact will then be at the cuspid as we finish the guidance to the left. The next movement that I'm going to demonstrate is protrusive, and I'm first going to show protrusion edge to edge. With protrusion edge to edge both lateral pterygoid muscles are contracting simultaneously. Now I'm going to model maximal protrusion. You'll see that the incisors go beyond the edge to edge position as the condyles translate out to the level of the eminence. Now the next thing that I would like to show is chewing from a hinge position on the right side. So I'm taking the mandible through the typical chewing movement to masticate in the right posterior dentition. And you can see how things are functioning with the normal disk alignment. Now I'm going to show a posselt sagital opening of the mandible. And, again, you can see the contact during the protrusive movement and full-tooth contact when the model closes fully down. Now as one example of what happens with diskal displacement, I'm going to show the sequences again with a dislocated disk alignment. So, here I've slipped both disks out of place, and you can see the occlusal contact is now changing, especially when I take the patient into the initial closing position you can see only the back teeth touch, and then on the protrusive movement in the posselt sagital you can see that the contact goes from posterior teeth to the anterior teeth. And, again, this is because of loss of vertical dimension inside the temporomandibular joint from the displacement of the disk.