Teeth and Occlusion
2.2.16 in General
We have been talking about the healthy human jaw. We know that the creator of this system had to account for an upright, reasoning, communicating, mammal using this jaw. Therefore, things like an open airway, ability to speak, and a way to begin digestion of nourishment became important. In other words, our jaws, muscles, and teeth and bone, need to allow us to breathe, speak and eat, without wearing out. That’s quite a daunting project for even the best engineer!
My last blog post, I talked about the muscles that move our jaws. These are known as the muscles of mastication because they enable us to “chew”.(another word for masticate). So, what would be the best way to design teeth, and house them in the jaw bone? And how do we correctly allow them to come together?
Typically humans have 32 teeth, 16 upper teeth opposing 16 lower teeth. These are arranged side by side on an arch form, and connect to the bone of the jaw by a sling of ligament around the roots of each tooth. This provides for a very rigid system of chewing tools that enables us to do the heavy work of chewing food. Yet, there is a built-in “shock absorber system, that allows forgiveness of position of each tooth, to minimize damage.
We know that the fulcrum of our jaws is the joint (furthest away from the food). Because the force to close the jaw (the muscles) is “in front” of the fulcrum, when we bite an apple, we are using a third –class lever to do so. The front teeth therefore receive the least force. So we can hinge on a healthy joint, and stop the closing movement when front lower teeth hit front upper teeth. If the back teeth are in a correct position, there should be no interference to this perfect harmony. One of my mentors says, “ we could place quail eggs in the back where the molars go, and closing the jaw would not break them.”
The ability to speak, smile, chew and breathe. What a perfect design! So why then do jaws “pop”, muscles ache, and teeth break? Ah, that’s for our next few discussions. Stay tuned in, and keep smiling. Dr. W.