TMJ Frequently Asked Questions
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What is TMJ?
Temporomandibular joint is the jaw joint and is frequently referred to as the TMJ. There are two TMJ’s, one on either side, working in unison. The name is derived from the two bones which form the joint, the upper temporal bone which is part of the skull, and the lower jaw bone called the mandible. The unique feature of the TMJ’s is the articular disk. The disk is composed of fibrocartilagenous tissue (like the firm but flexible cartilage of the ear) which is positioned between the two bones that form the joint. The disk divides each joint into two. The lower joint compartment formed by the mandible and the articular disk is involved in rotational movement (opening and closing movements). The upper joint compartment formed by the articular disk and the temporal bone is involved in translational movements (sliding the lower jaw forward or side to side). The part of the lower jaw which mates to the under-surface of the disk is the condyle (the round end of the lower jaw) and the part of the temporal bone which mates to the upper surface of the disk is the fossa ( or the socket ).
How does my jaw joint work?
The temporomandibular joint system is made of a combination of bones, muscles, cartilage, nerves and fluids that work together to permit movement. During jaw movements only the lower jaw moves.
The lower jawbone, or mandible, connects with the temporal bone at the side of the skull near the ear. Each side of the mandible has a rounded structure called the mandibular condyle. The condyle fits into a depression in the temporal bone called the fossa. Both the mandibular condyle and the fossa are covered with cartilage. A soft, thin, oval-shaped disc (articular disc) fits between the condyle and the fossa. The disc acts as a buffer between the mandibular condyle and the skull. The disc absorbs shock and smoothes jaw movements.
What is TMJ Disorder or TMD?
Pain or dysfunction of the temporomandibular joint is commonly referred to as “TMJ” when in fact, TMJ is really the name of the joint, and Temporomandibular joint disorder (or dysfunction) is abbreviated TMD. This term is used to refer to a group of problems involving the TMJ’s and the muscles, tendons, ligaments, blood vessles, and other tissues associated with them. Some practitioners might include the neck, the back, and even the whole body in describing the problems with the TMJ’s.
What causes TMD?
In most cases TMD is caused by a childhood growth asymmetry that does not allow the lower jaw (mandible) to fit center to the upper jaw (maxilla). Airway and posture have a strong effect on growth posture. Some other cause of TMD can be over use of the muscles like grinding or clenching, injury such as a car accident or any type of injury to the head, dentistry such as fillings or crowns that are not adjusted correctly into a patients bite, and poor treatment planning during orthodontics can freeze you into a pattern that will follow you through your life causing trauma to the TMJ. Osteroarthritis can also be a cause of TMD, it is a form of degenerative joint disease. In some cases muscle pain can be associated with TMD. Any dysfunction of the muscles may cause the teeth to occlude (bite) with each other incorrectly. If the teeth are traumatized by this they may become sensitive demonstrating one of the many interplays between muscle, joint and tooth.
Disc displacement is the most common disorder of TMD. This is when the articular disc moves from between the condyle (the round end of the lower jaw) and the fossa (socket) so that the bone if of the lower jaw and the temporal bone are touching, with nothing to cushion the constant movement of the jaw. On opening a “pop” or “click” can sometimes be heard or felt indicating the condyle is moving back on the disc. Upon closing the condyle will slide off the back of the disc causing another “pop” or “click” this causes to much pressure leading to inflammation and pain in the TMJ and the surrounding muscles. When there are multiple rough sounds “pop” or “click” it is described as “Crepitus”. When the joint is functioning properly, the disc stays in use, preventing the bony structures from coming in contact. When the joint is not functioning properly, the disc is commonly pulled forward when the jaw is in use, causing the bones of the skull and jaw to grind together.
Why are Airway Patterns so important to jaw function?
The simple answer is the bite grows into a skeletal asymmetry. The best example of a skeletal asymmetry in growth is one leg grows shorter than another. After years of walking off-sides, one knee or hip may age at an accelerated rate as compared to the other knee or hip from the stressed biomechanical function over time. When a child is chronically congested at a young age, the tongue and a hard swallow force the palate to vault. Prolonged thumb sucking does the same thing, forcing the palate to vault. (Kids suck their thumb to get oxygen to the brain as the thumb allows the tongue to relax from a hard swallow.) And as a result of a vaulted palate, there becomes a skeletal mismatch as the upper maxillary arch is in the shape of a “V” and the mandible grows in the shape of a “U”. A “U” doesn’t fit inside of a “V” so the bones grow off center and after millions of chewing cycles biomechanically one or both T.M. joints break down.
- Females are ten times more likely to have jaw disorders than men.
- Females turn or twist on their jaw ligaments – men compress their joints overtime.
- Pregnancy and lack of estrogen are related to T.M. ligament stress.
- Headaches are usually behind the eye when the patient wakes up in the am.
- Muscle tension headache is a very common precursor for migraine.
- Neck pain can be a factor years before the jaw pain arrives.
- Tinnitus and vertigo are common with jaw disorders.
- Clicking jaw joints before age 20 with headaches can set up a lifetime of chronic pain.
- Most jaw dysfunction cases take 10 years to flatten the disc.
- As disc’s flatten, the stress goes to the teeth in the form of cracks and sensitivity.
- Root canals and crowns on the clicking jaw side are common.
- Notches in the teeth at the gum line are diagnostic to lateral stress in the bite.
- Recession of the gums is diagnostic to lateral stress in a bite.
Basically, in the human body, systems grow, function and adapt in a magical way. However, a small skeletal asymmetry in the bones at a young age forces the anatomy to over adapt in time. Jaw joints are make to be loaded for a power chew, but jaw joints that do not center make the chewing patterns off center and now bones, ligaments, muscles and blood flow are not balanced.
The best analogy here is a car that needs the tires balanced. If one tire is losing air, the others wear down more from compensation. The wear is not in the center of the tire but on the sides due to excessive lateral stress in function.