The mandible is the largest bone of the face and the only bone in your skull that can move. The temporomandibular joints, located below your ears on either side of your head, allow you a range of motion so that you can speak, chew, swallow, yawn and move your jaw from side to side. Most people, including doctors and dentists, refer to this joint as the TMJ.
Because of the complexity of your TMJ anatomy, disorders and pain can be common. Let’s take a look at what makes up this joint.
Parts of the TMJ
As a review in the Journal of Manual & Manipulative Therapy explains, the lower jaw, also known as the mandible, has two vertical extensions from each side, with a condyle at the top. The condyle can be many shapes and asymmetrical. The TMJ is formed where the condyles meet the temporal bone of the cranium.
A fibrous disk, called the articular disc, cushions the space between these two bones and keeps them from touching. A synovial membrane, synovial fluid, blood vessels, and nerves, as well as connective tissue, are found in the area behind the articular disc.
In addition, three ligaments help stabilize the joint, prevent dislocation and support the weight of the mandibular bone.
Unique TMJ Anatomy Function
The TMJ is distinctive from other joints your body in that it permits both sliding and hinging action. It allows you to open and close your mouth, push your jaw forward, slide your jaw back and move it side to side. While the joint has the ability for this motion, the following muscles of mastication actually produce the movements.
- Masseter. This quadrangular shaped muscle is the most powerful of the four muscles of mastication. It has two parts and is responsible for lifting your mandible and closing your mouth.
- Temporalis. Besides lifting the mandible and closing your mouth, this muscle also retracts the mandible, which pulls it back posteriorly.
- Medial pterygoid. With a quadrangular shape, this muscle is both deep and superficial. Just like the masseter and temporalis muscles, it elevates your mandible and closes your mouth.
- Lateral pterygoid. This two-part muscle is shaped like a triangle and is largely responsible for sliding your jaw forward, but it also moves the jaw side to side.
All of these muscles are signalled into action by the mandibular nerve, which is a branch of the trigeminal nerve located in the brain.
Because of the complex makeup of the TMJ, almost 10 million Americans have some sort of problem with this joint, according to the National Institute of Dental Craniofacial Research. Women are affected more often than men. This may be because the makeup of the articular disc is different in women, and some studies believe it may also be affected by female hormones.
Complications and discomfort can be due to trauma to the jaw from injury or long-term grinding, muscle spasms from stress, misaligned teeth or some form of arthritis. The source of the problem isn’t always evident, but depending on the person many TMJ problems can resolve themselves with little or no treatment. However, you should always see your dentist whenever you notice pain or stiffness in your face, jaw, or neck, limited movement or locking of your jaw, or painful clicking or popping when you open or close your mouth.
Maintaining a Healthy TMJ
A good oral health routine that includes brushing twice a day with toothpaste and flossing daily is key to your oral health. By scheduling routine exams, your dentist can check your teeth and TMJ for signs of trouble. If you grind your teeth, they may recommend wearing a mouthguard.
The complexity of TMJ anatomy can be a bit daunting. But, when you know the basics of how your temporomandibular joint functions, it may help you better understand how you can keep it in good working order for many years to come.