Key points in brief
- Wisdom tooth coronectomy removes only the crown, the top of the tooth, and leaves the roots in the bone when extracting the whole tooth could injure the nerve beside them.
- The dentist checks where the roots lie on an X-ray, often also a CT scan. Coronectomy is usually not done on a dead tooth or with infection around the root.
- The remaining roots are checked for years. In some people a second procedure later removes them, and by then they usually lie further from the nerve than at first.
- After coronectomy, numbness of the lip is rare, and healing usually goes much the same as after surgical removal of the whole tooth.
- Call the practice straight away if pain or swelling gets worse after the procedure, lip or tongue numbness lasts longer than the anaesthetic, or a fever or pus appears.
Consult your case with an expert and get your treatment plan
Why a wisdom tooth near the nerve changes the treatment plan
When the dentist removes the whole tooth, a root lying right next to the nerve can press on it or partly tear it. This is the inferior alveolar nerve, which runs through a canal in the lower jawbone, below the roots of the teeth.
Nerve injury causes numbness of the lower lip and chin on the side of the procedure, sometimes tingling or burning. It usually wears off within weeks or months, but it is sometimes permanent. When the roots overlap the canal on the X-ray, temporary numbness after removal of the whole tooth happens in roughly 1 procedure in 12. Numbness that has not gone away after six months happens in roughly 1 procedure in 100, and more often when the X-ray shows clear signs that the root lies against the nerve. Sometimes the lingual nerve, which gives the tongue its feeling, is injured as well.
In wisdom tooth coronectomy, the dentist removes only the crown, the upper part of the tooth covered with enamel. The roots are left in the bone, so they do not have to be pulled out past the nerve. Much of the evidence suggests that the lip goes numb far less often after coronectomy than after removal of the whole tooth. The lingual nerve is also injured less often. The risk falls, but it does not disappear.
Most wisdom teeth, including those buried deep in the bone, are nevertheless removed completely during surgical wisdom tooth extraction. First, the dentist decides whether to remove or keep the wisdom teeth. Coronectomy is considered only when the tooth has to come out and the X-rays show the roots next to the nerve.
What to ask the dentist after looking at the X-rays
If the dentist has suggested a wisdom tooth coronectomy, or has told you that the roots of your wisdom tooth lie next to the nerve, these questions will help you understand the plan:
- Does the root touch the nerve canal, or is there still a layer of bone between them?
- What do I risk with removal of the whole tooth, and what with coronectomy?
- Is there anything about my tooth that rules out coronectomy?
- How often should I come for follow-up X-rays, and for how many years?
- What should I do if my lip starts to go numb after the procedure?
If your dentist has referred you to an oral surgeon, take your X-rays or CT scan to the consultation, ideally together with the files on a disc or in the cloud.
When wisdom tooth coronectomy is possible and when it is not
Coronectomy is considered for a lower wisdom tooth whose roots are clearly in contact with the nerve canal. The roots stay in the bone together with the pulp, the living tissue inside the tooth, so the tooth must be alive and the pulp healthy.
| Point | Removal of the whole tooth | Coronectomy |
|---|---|---|
| What stays in the bone | nothing | the roots, slightly below the edge of the bone |
| Risk to the inferior alveolar nerve | higher when the roots touch the canal | much of the evidence suggests it is clearly lower |
| Pain and swelling in the first week | typical after a surgical procedure | usually similar |
| Follow-up visits | usually until the wound has healed | usually an X-ray after the procedure, another after about a year, then at check-ups; the dentist checks that the roots are not moving towards the gum |
| Second procedure | not needed | in some people, sometimes after many years |
| When it is not chosen | often when the roots clearly touch the canal and the tooth is suitable for coronectomy | a dead tooth, infection around the root, a root that turns out to be loose during the procedure |
Coronectomy is usually not done when:
- the tooth has died or the pulp is inflamed;
- an area of inflammation is visible at the tip of the root, or a large cyst has developed around the tooth;
- decay reaches the root, or the root is being broken down from the outside;
- the wisdom tooth is the source of a severe infection.
Decay limited to the crown - as long as it does not reach the pulp - is usually not an obstacle, because the crown is removed anyway. In people with weakened immunity and after radiotherapy that included the lower jaw, coronectomy tends to be avoided.
Age alone does not rule out the procedure. Coronectomy is also carried out in people over 60, including those with long-term illnesses and those taking anticoagulants (blood thinners). If you take such medicines, tell the dentist about them and do not stop taking them on your own.
In young adults - up to about the age of 25 - the roots move more often after coronectomy. In addition, permanent nerve injury after removal of the whole tooth is less common in them than in older people. That is why, in this age group, coronectomy is considered only when there are clear reasons for it.
How the dentist assesses the risk on an X-ray and a CT scan
The first test is a panoramic X-ray, an ordinary X-ray of all the teeth and both jaws. On it, the root and the nerve canal overlap, so it cannot be seen whether they touch or only lie one behind the other. The dentist therefore looks for signs that the root lies next to the nerve:
- the root looks darker where it crosses the canal;
- the white line outlining the nerve canal is interrupted;
- the canal narrows or changes direction near the root;
- the root narrows or bends near the canal.
These signs are also seen in many people whose nerve remains unharmed after the procedure. That is why the dentist does not base the decision on any one of them. When there are several such signs, or one of them is clear, the dentist usually orders a cone-beam CT scan. This is a 3D scan that shows the root and the canal in cross-section.
On the CT scan, what tells the dentist most is whether a thin wall of bone surrounding the canal is still there between the root and the nerve. In the CT report, the nerve canal is usually called the mandibular canal, and this wall the cortical plate. Its absence is described as an interruption of the cortical plate.
In people at higher risk in whom this wall was visible, nerve injury after removal of the whole tooth was very rare. When it was missing, nerve injury affected roughly 1 person in 6. So a missing wall speaks in favour of wisdom tooth coronectomy, and a visible wall - even when the ordinary X-ray looks worrying - usually in favour of removing the whole tooth.
How wisdom tooth coronectomy is done and what the first days are like
Removing the crown of a wisdom tooth is a dental surgery procedure that the dentist carries out under local anaesthetic. First the dentist exposes the tooth, cuts the crown off where it joins the roots and lifts it out. The roots are trimmed so that they lie slightly below the edge of the bone. Finally, the dentist checks that the roots are not loose and stitches the gum.
If a root turns out to be loose during the procedure, the dentist removes it completely there and then. This is rare, but the risk to the nerve is then higher than when the roots stay in the bone. This is exactly why, before the procedure, the dentist discusses both options with you: coronectomy and removal of the whole tooth. Your consent should cover both possibilities.
Much of the evidence suggests that dry socket, a painful inflammation after the blood clot is lost, does not happen more often after coronectomy than after removal of the whole tooth. Wound infection occurs about as often. Advice on antibiotics varies, so the dentist will tell you whether you need one in your case. The rules on brushing, rinsing and physical effort in the first few days are the same as in tooth extraction aftercare. zaleceniach po usunięciu zęba.
What happens to the roots left in the bone
In coronectomy, the dentist leaves the roots in the bone on purpose and plans their follow-up from the start. The situation is different when the whole tooth is being removed and a piece of root breaks off by accident.
Roots left in the bone usually do not stay put. Within the first year they move in roughly 7 cases out of 10, usually upwards by a few millimetres. The movement is greatest in the first year and then usually slows down.
This movement has an upside: if the roots ever need to be removed, they lie further from the nerve than before the first procedure. It can also cause trouble, because a root may come close to the surface of the gum and become exposed. You can then feel something hard in the gum, or the gum in that spot becomes tender and red. Let the practice know. Such roots are often removed in a second procedure.
Less often, the trouble is an infection around the roots. If it does not clear up with treatment, the roots are removed.
It is not possible to predict in advance who will need a second procedure. That is why follow-up X-rays after wisdom tooth coronectomy apply to everyone, including people whose first year passed without problems. If you change dentists, tell your new dentist that you have roots left in the bone after a coronectomy.
Late problems are rare, but they can occur even many years later. Very rarely, numbness of the lip appears only some time after coronectomy. If you notice it, contact the practice without waiting for your follow-up visit.
What to settle with your dentist before deciding on coronectomy
Wisdom tooth coronectomy usually reduces the risk to the nerve, but in return it requires follow-up over the years and sometimes a second procedure. Before you decide, ask the dentist whether the root is in contact with the nerve canal and whether the tooth is suitable for the procedure. Before the procedure, agree on when you will come for your first follow-up X-ray. Report numbness of the lip or tongue, increasing pain or swelling, a fever or pus after the procedure straight away, without waiting for your follow-up visit.
Frequently asked questions
Are the roots left in the bone safe?
The roots left in the bone are usually safe and in most cases cause no problems for years. They stay there together with the living pulp, the tissue inside the tooth. They are not given root canal treatment, because much of the evidence suggests that such treatment does not reduce the risk of infection. The roots are left only when the tooth is alive, with no inflammation at the root and no decay reaching the root.
Can my lip go numb after coronectomy?
Numbness of the lip after coronectomy is possible, but rare. It happens after roughly 1 to 2 procedures in 100, or less often. It is not yet known how often this numbness goes away on its own. If numbness lasts longer than the anaesthetic, or appears later, report it straight away, without waiting for your follow-up visit.
Does coronectomy hurt less?
Pain and swelling after coronectomy are usually similar to those after removal of the whole tooth. Most studies do not show that coronectomy hurts less. Pain may last a little longer, although the difference is small. Coronectomy is chosen to protect the nerve, not for gentler healing.
Do I always need a CT scan before coronectomy?
No. A cone-beam CT scan (CBCT), a three-dimensional X-ray, is ordered when the ordinary X-ray shows signs of close contact between the root and the nerve, and the result could change the choice between coronectomy and removal of the whole tooth. It is not ordered for everyone, because in most studies having the scan did not by itself reduce the number of nerve injuries, and the radiation dose is several times higher than for an ordinary X-ray.
How often is a second procedure needed after coronectomy?
In the first few years after coronectomy, a second procedure is needed for a few teeth in 100. Over 10 years, roughly one tooth in eight may need it. The most common reason is a root that has moved upwards and become exposed in the gum, and less often pain or infection around the roots. This second procedure usually does not damage the nerve.
What is healing like in the first week after coronectomy?
Pain is usually at its worst on the first day and then eases. Swelling of the cheek is greatest in the first 2 days, and difficulty opening the mouth may still increase on the second day. At the end of the week, some people still have symptoms. Pain that starts getting worse again, swelling that increases after day 3, a fever, pus, or numbness of the lip or tongue are reasons to call the practice straight away.
How often are the roots left in the bone checked in later years?
Usually the dentist takes an X-ray soon after the procedure and another after about a year, because the roots move most in the first year. After that, the area is checked at routine check-ups, because a root can become exposed even in the 8th or 9th year. There is no single agreed schedule, so the dentist will set the dates with you. [CLINIC DATA: follow-up schedule after coronectomy at Modern Dental & Orthodontics]
Read more:
- Dental Surgery in Warsaw Wola
- Wisdom teeth — remove or keep? A comprehensive extraction guide
- Dental radiographs, panoramic imaging, 3D tomography: A guide to dental radiology
- Tooth extraction aftercare: washing your hair, sleeping, work, sick leave and smoking
- Blood clot after tooth extraction — what a normally healing socket looks like
Content and liability disclaimer
This article is informational and educational in nature and does not constitute medical advice, a diagnosis or a therapeutic recommendation — it does not replace a consultation with a specialist. If you are experiencing symptoms, have doubts or are facing a decision about treatment, consult a dentist. The methods described and the data cited are general in nature. The results of scientific studies relate to populations, not to an individual patient. The course and outcome of therapy depend on the individual clinical situation and may vary between patients. No information contained in this article constitutes a guarantee of result. The content has been prepared with due care, based on publicly available medical knowledge and the scientific publications indicated in the Sources section. We do not advise taking or refraining from any health-related action solely on the basis of the content of this article, without prior consultation with a doctor.
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