THE BONES: There are two movable joints in the face. The right and left temporomandibular joints. (TM joint or jaw joint). The TM joint is formed by two bones; the temporal bone and the mandible. It is located in front of the ear. By placing your fingers in front of your ear and opening your mouth, you can feel the joint move. The part of the mandible in the joint, the condyle, glides along the surface of the temporal bone as the mouth opens. Between these two bones is an articular disc.
THE DISC: The articular disc, situated between the bones of the joint is surrounded by fluid. It cushions the forces between the bones allows for smooth motion during opening and closing. If it is displaced it can cause clicking or jaw locking.
LIGAMENTS: The disc and mandible are attached to the skull by ligaments. If the ligament gets stretched out the disc becomes displaced. It was once thought that ligaments could not heal if damaged. We now know that the ligaments in this joint can heal very well. Under the right conditions the ligament can produce a second disc to replace the damaged one.
MUSCLES: The muscles under the skin of the face are divided into two categories, supplied by two different nerves. The muscles responsible for jaw movement when we eat and talk are called muscles of mastication. The other group is called muscles of facial expression which are responsible for showing our emotions, by smiling or raising our eyebrows. It is usually the muscles of mastication that are involved in producing the pain of TMD.
NERVES: The face, head and neck contain a multitude of nerves. Sensory nerves convey information about our environment, such as hot, cold pressure and pain. The motor nerves are connected to muscles. Stimulation of motor nerves causes muscles to contract.
The two most important nerves of the face are the trigeminal which is mostly sensory and the facial which is mostly motor. The trigeminal nerve goes to the teeth. The facial nerve controls the muscles of facial expression. It is usually the trigeminal nerve which is involved in orofacial pain.
