What is it?
A cyst is a cavity that forms inside the jawbone, filled with fluid or soft tissue and lined by a membrane. Most arise from the tissue a tooth develops from, or from inflammation at the root tip of a tooth that has lost its nerve. The pressure inside slowly pushes the surrounding bone aside and widens the cavity.
Because it grows slowly, pain is usually not present. A cyst only gives symptoms once it has thinned the bone enough to be felt from the outside, has shifted the neighbouring teeth, has pressed on a nerve and caused numbness in the lip, or has become infected. Until that point its only sign is a dark, clearly outlined area on an X-ray.
Not every dark area on an X-ray is a cyst; some benign tumours and developmental cavities give a similar picture. This is why the definitive distinction is made by examining the removed tissue in the laboratory. Naming the type from the image alone would not be right.
Signs
You will not necessarily have all of these at once.
Why does it happen?
- 01
Long-standing inflammation at the root tip
At the root tip of a tooth that has lost its nerve, a granuloma can form first and a cyst can develop over time. This is the most common type, and it is not expected to disappear unless the tooth it comes from is treated.
- 02
The sac around an impacted tooth
The sac around a tooth that has not come through, particularly a lower wisdom tooth or an impacted canine, can fill with fluid and expand. This type can grow for years without giving any sign.
- 03
Remnants of developmental tissue
Cell remnants left over from tooth development can form a cyst within the jawbone. Some of these tend to come back after removal; this is why telling the types apart matters.
- 04
Trauma and previous surgery
Cavities that form inside the bone after a blow, and tissue left behind by earlier surgery, can also create a similar appearance. The distinction is made with imaging and laboratory examination.
How does it progress?
- Most common
Root tip cyst
This develops at the root tip of a tooth that has lost its nerve. The source tooth is either saved with root canal treatment or taken out; the cyst cavity is usually dealt with at the same appointment.
- Impacted tooth
Dentigerous cyst
This develops from the sac that surrounds the crown of a tooth that has not come through. It is seen most often around a lower wisdom tooth or an upper canine; the treatment plan is built by assessing the cyst and the tooth together.
- Can come back
Odontogenic keratocyst
This grows lengthwise through the bone from front to back and tends to come back after removal. Radiological follow-up spread over years is part of the treatment for this type.
- Look-alikes
Other findings that look like a cyst
False cavities within the bone and some benign tumours resemble a cyst on an X-ray. The distinction only becomes clear once the tissue taken has been examined.
How is it treated?
Treatment is planned according to the type of cyst, its size and its relationship to the structures around it. In small cysts with a clear source, treating or taking out the tooth along with removing the cyst in one piece is enough. The tissue removed is sent for laboratory examination in every case.
In large cysts, or where structures such as the nerve in the lower jaw or the sinus floor are close by, opening the cyst into the mouth to let it shrink first may be preferred. The cavity narrows over months, and what remains is then removed with less risk. In some cases a graft is placed in the bone cavity left behind.
Follow-up is part of the treatment. Radiological review spread over years is planned, particularly for the types that tend to come back. Once the bone has finished healing, the plan for an implant or a prosthesis is assessed again.
- Numbness in the lip or chin that has just started
- A jaw swelling that is hard, painless and growing quickly
- Redness, fever and pain being added to a swelling
- Teeth shifting position or becoming loose over a short period
How is it prevented?
- Have a panoramic X-ray at the intervals your dentist advises, not only when something hurts; most cysts are picked up on these images.
- Do not let teeth that have lost their nerve, or root canal treatments left half finished, drag on.
- Have impacted wisdom teeth, and adult teeth that do not come through on time, monitored regularly.
- If you notice hardness or swelling in your jaw, or teeth shifting position, have it examined without waiting for pain.
Frequently asked questions
- Does a cyst go away on its own?
- That is not expected. Because the pressure inside pushes on the bone, cysts tend to grow over time. When the tooth at the source is treated, small lesions at the root tip can be seen to shrink; this is monitored with X-rays taken at intervals.
- Is a jaw cyst cancer?
- The great majority of jaw cysts are benign. Even so, the appearance on an X-ray is not enough on its own to tell one type from another. Examining the removed tissue in the laboratory both identifies the type and gives information about the risk of it coming back.
- Is the tooth lost as well when a cyst is removed?
- Not always. If the source tooth can be saved, it can be kept with root canal treatment. In a cyst that develops around an impacted tooth, the tooth is usually taken out as well. The decision is made according to the relationship seen on the X-ray and the state of the tooth itself.
This content is for general information and does not replace an in-person examination. Symptoms overlap between conditions, and a diagnosis can only be made clinically.