Short answer: In disc displacement with reduction, the disc in the jaw joint slips forward when the mouth is closed and settles back into place with a click as the mouth opens; mouth opening is usually preserved. In disc displacement without reduction, the disc cannot return to its place, the click often disappears and mouth opening becomes limited. A click that causes no pain may not need treatment in most cases; the decision on evaluation and tests is made through a dentist's exam.
A "click" coming from right in front of your ear when you open your mouth, or your jaw not opening fully when you wake up in the morning, is often related to the position of a small disc in the jaw joint. The medical term for these conditions is disc displacement, and it comes in two main forms: disc displacement with reduction and disc displacement without reduction. Although the names look complicated, the difference between them is quite simple: can the disc return to its place as the mouth opens, or can it not? In this article, we explain what the jaw joint disc is, how the two conditions are told apart, which symptoms matter and how the dentist's evaluation proceeds.
What is the jaw joint disc?
The jaw joint disc is a thin cushion made of fibrous cartilage that sits between the head of the lower jaw bone and the joint socket in the skull. This joint, called the temporomandibular joint (TMJ), is located right in front of the ear and works in all everyday movements such as talking, chewing and yawning.
The disc prevents the two bone surfaces from rubbing directly against each other and helps the movement stay smooth. In a healthy joint, the head of the joint glides forward as the mouth opens, and the disc moves along with it. When the ligaments and surrounding tissues that hold the disc in place loosen or are strained, the disc can slip out of its normal position, most often forward and inward. This condition is called jaw joint disc slippage or disc displacement.
What is disc displacement with reduction?
Disc displacement with reduction is the condition in which the disc, which is slipped forward when the mouth is closed, settles back over the head of the joint as the mouth opens. The word "reduction" here refers to the disc returning to its place.
During this return, most people hear a distinct click in front of the ear or feel a jump with their finger. Because the disc slips forward again as the mouth closes, a milder second click can occur on closing; this is called a reciprocal click. Mouth opening is usually within normal limits, but the jaw may briefly deviate to one side during opening and then return to the center.
An important piece of information: in a significant proportion of people in the general population who have a click from the jaw joint, there is no pain or limitation of movement. A click that does not cause pain or loss of function may not need treatment on its own in most cases; simply monitoring it can be enough. A dentist's exam is still needed to make this decision. In some people, episodes of intermittent locking may occur in which the disc settles into place late and the jaw "catches" for a short time; this is a sign that needs to be monitored more closely.
What is disc displacement without reduction?
Disc displacement without reduction is the condition in which the disc, which has slipped forward, cannot return to its place as the mouth opens and forms an obstruction in front of the head of the joint. Because the disc does not settle into place, the earlier click often disappears, but mouth opening becomes limited.
This picture accounts for some of the conditions known in everyday speech as jaw locking; in medical language it is also called "closed lock." The person cannot open their mouth as wide as usual, the jaw deviates toward the affected side when opening, and side movements to the opposite side can become difficult. In the newly started (acute) period, the limitation can be marked and bothersome. Over time (in the chronic period), as the tissues adapt, mouth opening may partially increase; however, this process does not progress the same way in everyone.
The disc is not the only cause of jaw locking; different situations such as muscle spasm, infection or the period after a tooth extraction can also limit mouth opening. We covered this topic separately in our article on trismus and jaw locking.
Symptoms: clicking, locking, pain
The most common symptoms of disc displacement are a click from the jaw joint, limited mouth opening and pain around the joint; however, not everyone has all of these symptoms together. The type of symptoms gives an idea of which type of displacement may be involved.
- Jaw joint click: A clear click heard especially as the mouth opens is often associated with displacement with reduction. Grating sounds that resemble crushing sand, on the other hand, may point to different joint changes.
- Locking: The mouth suddenly not opening fully, or having difficulty closing when open. In someone who previously had a click, the sound stopping and mouth opening decreasing is a change that needs attention.
- Pain: It may be felt in front of the ear, at the temple or in the chewing muscles; it may increase with chewing, yawning or in the mornings.
- Conditions that may accompany it: Teeth clenching or grinding, headache and a feeling of fullness in the ear may accompany the picture in some people.
How is it diagnosed?
The evaluation of disc displacement is done primarily with a detailed history and a clinical exam; the need for imaging is decided by the dentist according to the exam findings. Diagnosing yourself or drawing conclusions from the presence of a sound alone is not right.
In the exam, mouth opening is generally measured, the path the jaw follows during opening is observed, the joint and chewing muscles are palpated and the moment at which sounds occur is assessed. The bite of the teeth and signs of wear caused by clenching are also examined.
The method that can directly show the position of the disc is magnetic resonance (MR) imaging. However, an MRI is not needed for every click. If symptoms are persistent, mouth opening is limited, complaints continue despite treatment or an advanced intervention is planned, the dentist may request an evaluation with MRI. When the bony structures need to be examined, different imaging methods may be preferred. Which test is needed is determined entirely by the dentist after the exam.
What are the treatment options?
In disc displacement, treatment in most cases begins with conservative and reversible methods; more advanced interventions come up only when sufficient relief cannot be achieved with these methods. The aim is not necessarily to return the disc to its old position, but to reduce pain and make jaw movements functional.
- Information and daily habits: Eating soft foods for a while, avoiding chewing gum and opening the mouth too wide, supporting the jaw when yawning, and noticing and stopping the daytime clenching habit.
- Warm or cold application and exercises: Simple jaw exercises recommended by the dentist or physiotherapist can help relax the muscles and regulate movement.
- Splint (night guard): Especially when clenching and grinding accompany the problem, a custom-made occlusal splint can help reduce the load on the joint and muscles. For details, you can look at our article on splint treatment.
- Medication: In painful periods, the dentist may recommend suitable medications for a short time. The choice of medication and the duration of use are specific to the person; using medication on your own is not recommended.
- Arthrocentesis: Especially in displacement without reduction, if mouth opening remains limited despite conservative methods, this procedure, based on washing out the joint space, may be considered. More information is in our article on arthrocentesis and jaw joint injection.
- Surgery: In a very small number of patients, in selected cases where other methods are not sufficient, it is evaluated by the relevant specialty.
You can find the general framework of the conservative approaches applied at our clinic on the page about TMJ treatment and methods for relieving the jaw joint. For people who are considering orthodontic treatment and have complaints in the jaw joint, our article on clear aligners and the jaw joint may also be a guide; in such cases, it is important to evaluate the joint before treatment.
What is the difference between disc displacement with and without reduction, in brief?
The basic difference between the two conditions is whether the disc returns to its place as the mouth opens. In disc displacement with reduction, the disc settles into place on opening; for this reason, the click is distinct and mouth opening is generally preserved. In disc displacement without reduction, the disc cannot settle into place; the click often disappears, but mouth opening becomes limited and the jaw deviates to one side as it opens. In both cases, the severity of pain can vary greatly from person to person.
When should you see a dentist?
It is appropriate to see a dentist if the sound from the jaw joint comes with pain, if you cannot open your mouth as wide as before, if your jaw catches in the open or closed position, or if eating and talking have become difficult. A click that causes no pain and has not changed for years is not considered an emergency; even so, it is useful to mention it to your dentist at your next dental exam. At our polyclinic in Park Oran Ofis, next to Panora Mall in Çankaya, Ankara, jaw joint complaints are evaluated with an exam; whether imaging or referral to another specialty is needed is shared with you after this exam.
Frequently asked questions
Does every click from the jaw joint need treatment?
No. A click that does not cause pain or limitation of movement can in most cases simply be monitored. If pain, locking or difficulty opening the mouth accompanies the sound, a dentist's exam is recommended.
Can disc displacement with reduction become disc displacement without reduction?
In some people, it can become harder for the disc to return to its place over time and the picture can change; however, this is not seen in everyone. If changes such as the click suddenly stopping and mouth opening decreasing are noticed, it is appropriate to see a dentist.
Is an MRI absolutely necessary for disc displacement?
It is not. The evaluation is done primarily with a clinical exam. If symptoms are persistent, mouth opening is limited or an advanced intervention is planned, the dentist decides whether an MRI is needed.
Does a splint help in disc displacement?
Especially when clenching and grinding accompany the problem, a custom-made splint can help reduce the load on the joint and muscles. Whether a splint is suitable and how long it should be used is determined after the exam.
If my jaw locks, should I force it open?
Trying to force the jaw open can irritate the tissues more. In a sudden lock, it is a better approach to eat soft foods, rest the jaw and see a dentist soon.
