what is tmj
TMJ is the first letters of the three anatomic parts of the head. T = Temporal bone (skull), M = Mandible (lower jaw), J = Joint (connects two bones together) and called temporo-mandibular-joint. Between the temporal bone of the skull and the condyle of the mandible is a disc similar to the ones between your backbones. This disc is made of layers of hyaline cartilage, which is non-blood vessels and non-nerve tissue and covered by dense fibrous connective tissue, which has repair potential when damaged. This disc acts as a third bone within the joint and performs compressive movements.
TMJ has a dense anatomy of nerves, muscles, blood vessels, ligaments, tendons, sympathetic fibers, and synovial fluid within a small joint socket. All body joints (hip, knee, wrist, ankle, finger etc.) have either hinge movement or circular movement, or a combination of the two. However, TMJ has not only hinge and circular movement, but also has sliding movement, which moves in and out of the joint socket. There are two TM joints in the mandible but they move as one piece. Thus, if one joint is injured or out of joint socket, the other joint will usually become affected.
TMJs are associated with many small muscles and are held together by a group of ligaments. These muscles and ligaments can be damaged, and the disc can become displaced. Like other joints of the body, the TM joints can experience similar diseases and injuries found in other joints of the body and are vulnerable to injuries. If this delicate and sensitive joint complex receives constant distress, this can cause trauma and damage to the joint components and eventually manifest various pain and dysfunctions to the body.
The function of the TMJ is to hold the jaw within a certain boundary and guide the jaw movement in chewing, talking, singing, yawning, and swallowing etc. It also keeps open the airway for breathing while you are asleep. TMJ may be the second most moving part in our body next to the heart. An average person moves the TM joint 2,000-2,500 times a day and, if someone likes to talk or chew gum, it may move 5,000 times or even 10,000 times a day. Surprisingly, even with this much movement, the TM joint can function a lifetime with proper maintenance and balance.
However, TMJ is the least respected joint in the human body because of a lack of understanding of its complex anatomical structure, complicated internal mechanical movements, mysterious influence to the body function and health, and difficulty in correcting, treating and managing when it is in disorder and develop TMJ symptoms.
what is tmj disorders
Medical-Dental researchers and clinicians all agree that there are multiple causes for TMJ disorders. Some known causes are: malocclusion (a bad bite), bruxism (grinding teeth), para-functional habit (chewing gum, fingernail bite, pencil bite, habitual clenching, habitual jaw support on one side, using one side for a prolonged period of time etc.), post major surgery, scar tissue, automobile accident, whiplash, falls/injury, trauma (macro and micro) to the jaw, underdeveloped dental arch, structural imbalance (short leg, short arm), mal-alignment of spine, chronic stress related clenching/grinding, degenerative arthritis, emotional/psychological related stress, internal organ dysfunction, nutritional imbalance, toxic deposit, viral/bacterial infection, poor posture, and more unidentified factors. In other words,
“Anything can cause TMJ disorders”.
The fact is, “TMJs are inert objects”. They are not capable of initiating any movement on their own until attached muscles are contracted and pull it to move. If TMD symptoms begin to develop, it must be a result of unusual muscular activities beyond their adaptable capacity. So, the next question which must be asked is: What causes the muscles to come to this state? Muscles or ligaments do not have an intelligence of their own; they can only do what they are told to do by the nerves which control them. Therefore, with the exception of cases that have seen some type of severe blow to the jaw or accident, a muscular imbalance, with consequential joint distortion, must be caused by a neurological disturbance, which results in spasmodic muscles. The next question which must be asked is: What causes the neurological disturbance and what nerves are involved? The answer is: Dental Distress Syndrome and Trigeminal Nervous System.
DENTAL DISTRESS SYNDROME
Teeth are inserted into the jaw bone and at the end of the jaw is TMJs. The ligaments, tendons and muscles of TMJ which hold the jaw to the skull are small and very delicately balanced. If chronic distress is placed upon them and distract the adaptive limit to the muscles and joint, it goes into a protective spasm (cramp). This continuous spasm can become part of a cycle: muscle tenderness, pain, and more spasm, that results in tissue damage. Any dental distress, which disturbs the harmony of this complex “neuro-musculo-skeletal system” (nerves, muscles, bones and joints working together in harmony), can result in TMJ Disorder.
MALOCCLUSION (BAD BITE)
The number one cause of dental distress syndrome is malocclusion. TMJ position is established by the upper and lower arch relationship. This relationship is dictated by the bite of the teeth. If you have a physiologically functionally well balanced bite, you may not notice any discomfort, dysfunction or pain while joint is in move. However, if you have a bad bite, this can cause dental distress and forces TMJs to move to a non-physiologic position.
WHAT IS BAD BITE?: deep bite, missing molar teeth, multiple missing teeth, poorly aligned teeth, crooked teeth, badly decayed or broken teeth, excessively worn down teeth, loose teeth, poor dental work, poor orthodontic treatment, etc. Every time we chew, swallow, move head around, walk, work, drive, exercise, play, lift things up, and even during breathing and fall asleep, the upper and lower teeth constantly meet together lightly or clench hard. If there is a bad bite, this not only distresses to the trigeminal nervous system, but also forces the TMJ to move away from its balanced physiologic position. (Note: Not all bad bite cause TMJ disorders, and this is one of the big debates among dental professionals.)
Following is excerpted from Edwin A. Ernest, III, DMD’s article: “The ‘bite’ aspect of the term describes the influence of the upper and lower teeth. This influence includes the ‘fit’ of the upper and lower teeth and whether that fit helps to support or hinder the articulation of the jaw joint and thus its stability. In fact, it is accurate to describe each tooth in the maxillary bone and in the mandible to also be a ‘joint.’ In the human adult, anywhere from 28 to 32 teeth normally play a pivotal role in the health and or disease of the TMJ. An injury to a tooth affecting its position of height, maloccluded teeth, tooth extraction and progressive dental instability, extrinsic injury to the muscles or ligaments that move the joint, or internal derangement within the joint can all alter normal joint arthrokinesis. Arthrokinesis is the ligamento-neuro-muscular reflex mechanism that allows a movable joint anywhere in the body to work either effectively or to exhibit some degree of dysfunction, injury, or disease. In arthrokinesis, it is the ligament — via its mechano-receptors — that directs spinal and CNS activity that serves to protect as well as signal joint-related injury. Joint-related injury often results in muscular reflex restriction and pain, and the pain often includes pain referral to distant sites.”
TRIGEMINAL NERVOUS SYSTEM (TNS)
The trigeminal nerve (fifth cranial nerve) is the largest cranial nerve among twelve cranial nerves, has three branches, innervated with all other cranial nerves and directly innervated to all teeth, upper jaw, lower jaw, mouth, gums, tongue, nose, eyes, ears, face, head, and neck region. Trigeminal nervous system is associated with brainstem’s reticular formation function, which influences to autonomic nervous system, limbic system, hypothalamus and cerebellum. Additionally, resent EMG (electromyogram) research is demonstrating that postural stability of the head on the neck can be influenced by a TMJ problem or, conversely, the TMJ can be affected by changes in the axial cervical structures.
If any healthcare practitioner knows how to conduct and harmonize these three distinctive part of our body; trigeminal nervous system, occlusion (bite), TMJ he/she may be able to provide to the entire body its maximum performance in function and pain free condition. Bite changes throughout one’s lifetime and so does the TMJ balance.