A new study looking at the evolution of the temporomandibular joint shows that it’s mostly the size of the animal and not its diet that determines the shape, size, and strength of the jaw. Researchers hope that this will give us insight into temporomandibular joint disorders (TMJ or TMD), helping to improve diagnosis and treatment.
For this study, researchers looked at the skulls of 40 different species belonging to the order Carnivora, the largest order of mammals. This order includes species as diverse as cats, dogs, badgers, bears, and seals. They can be small like mongooses and large like walruses. Researchers felt that looking at the diversity in this order should reveal whether jaw structure was related to diet.
Researchers took the skulls of their selected species and performed CT scans of the skull, allowing them to produce 3D models of the skulls, complete with bone density modeling. They were then able to print out versions of the skulls that were scaled to model the proportional strength of the different jaws. In particular, researchers were focusing on the condyle of the temporomandibular joint. The condyle is the rounded knob on the jaw that attaches to the skull.
Researches expected to see animals like a hyena, which is partly a scavenger that cracks and grinds bones with its teeth, would have a much sturdier condyle than a panther, which mostly eats flesh and doesn’t crush bones.
However, they found that the jaw joint structure was mostly related to the size of the animal, not its diet. Hyenas didn’t have sturdier skulls. In fact, the relatively slight cheetah had the second strongest condyle (after the wolverine).
Because of this, they postulated that jaw joint development was governed in part by the size of the animal, and in part by other factors.
Why the Human Jaw Is Vulnerable
This new research shows us that our diet isn’t primarily responsible for the overall shape of our jaw, although the food we eat can impact the development of our jaw. Instead, the shape and sturdiness of our jaw is determined by other factors. In people one of these other factors is language use.
Many features of our jaw are influenced by our need to speak. The angle between our jaw and our throat, the position of our larynx, the shape of our mouth, the size of our tongue, are all linked in part to our need to speak. These features not only make us vulnerable to TMJ, but also to sleep apnea.
But perhaps the most important feature of the temporomandibular joint that makes it vulnerable to disorders is its complexity. Many people think this joint is a simple hinge that moves up and down, but if you take the time to explore it, you’ll notice that your jaw joint can move in many different ways. Your jaw can move forward and back, side to side, and even tilt on its axis.
Being free to move in all these directions leaves lots of room for disorders, such as tilt caused by uneven bite force and tooth wear, or displacement of the cushioning disk from inside the jaw joint.
These disorders can then spread through the body, either by impinging on nearby structures (ear, throat, nerves), by forcing the body to accommodate for the disorder, or by sharing tension with muscles in the head and neck.
Are You Experiencing Jaw Problems in River Edge?
If you are in River Edge, NJ, and you have or suspect you might have TMJ, we can help. TMJ dentist Dr. Marlen Martirossian has been trained to diagnose TMJ. He can provide noninvasive and drug-free TMJ treatments that can relieve your symptoms, such as headaches and ringing in the ear.
To learn whether TMJ treatment can help you, please call (201) 343-4044 today for an appointment at the River Edge Dental Center for TMJ, Sleep Apnea, & Reconstructive Dentistry.
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