Impacted wisdom tooth: should it come out, or can it wait?

Wisdom teeth usually come through between the late teens and the early twenties. If there is no room left in the jaw, the tooth becomes impacted by lying on its side, tilting forwards or staying completely inside the bone. Some show only one corner above the gum; this is called partially impacted. The NHS writes that when there is not enough room, wisdom teeth can lead to problems such as pain and swelling, gum infection, food getting trapped, decay, gum disease, cysts and abscesses, but that a tooth causing no problems is usually left in place and monitored.

For many years, the common practice was to remove impacted wisdom teeth early so that they would not cause problems. In 2000, NICE published a clear decision on this: the preventive removal of impacted wisdom teeth with no sign of problems should stop, and surgical removal should be limited to patients with a sign of disease. Plaque building up on the tooth is counted as a risk factor, but not as a reason for surgery on its own.

The body of evidence has not changed this decision. A 2020 Cochrane review concluded that there is not enough evidence to decide whether impacted wisdom teeth that cause no symptoms and show no signs of disease should be removed or kept. The same review notes that keeping these teeth may be linked in the long term to a risk of gum disease in the neighbouring second molar (based on a single observational study following 416 healthy men), but that the certainty of this evidence is very low. The review's recommendation is that the decision be made together with the patient's preferences and the dentist's clinical judgement, and that if the tooth is kept, it be checked at regular intervals.

A reason you often hear is that wisdom teeth push the front teeth and cause crowding. In the only randomised trial in the Cochrane review, removing impacted wisdom teeth that caused no symptoms in young people who had previously had orthodontic treatment had no clinically meaningful effect on the dimensions of the dental arch after five years. This study has a high risk of bias; even so, there is no strong evidence supporting having a healthy wisdom tooth removed to prevent crowding.

The findings that call for removal are listed one by one by NICE: decay that cannot be treated, inflammation inside the tooth or at the root tip that cannot be treated, inflammation spreading to the face (cellulitis), abscess and bone inflammation (osteomyelitis), root resorption of the tooth itself or of the neighbouring tooth, fracture of the tooth, disease of the tooth sac such as a cyst or tumour, teeth that get in the way of jaw surgery, and teeth within the field of tumour surgery. For pericoronitis, NICE's measure is this: a first episode, especially if it is not severe, should not be counted as a reason for surgery; second and later episodes, however, are accepted as an appropriate reason for removal. NICE also states separately that it is not clear how far the number and severity of episodes should influence the decision.

With a lower wisdom tooth, the risk talked about most is the nerve that runs through the lower jaw and carries sensation to the lower lip, the chin and the teeth (the inferior alveolar nerve). A nerve carrying sensation to the tongue (the lingual nerve) also runs along the side of the tongue. In a review combining 23 studies and 44,171 lower wisdom tooth extractions, temporary numbness of the lower lip and chin developed in 1.20 per cent of extractions and permanent numbness in 0.28 per cent. The factors that increased the risk were how deep the tooth was, whether the root touched the nerve canal, the surgical technique, the nerve being exposed during surgery, and the surgeon's experience.

That is why a panoramic X-ray is the first step. On the X-ray, darkening of the root where it overlaps the nerve canal, interruption of the canal's white border line and the canal changing direction are accepted as signs showing an increased risk of nerve damage. But the absence of these signs is not enough to rule out the risk: in a meta-analysis looking at panoramic signs, the sensitivity of the signs stayed between 6 and 49 per cent. Where the situation looks risky, the dentist may ask for a three-dimensional scan (cone beam computed tomography, CBCT). The scan shows the relationship between root and nerve more clearly, but in a meta-analysis combining 6 studies, having a scan before removal did not reduce numbness after removal compared with a panoramic X-ray alone. The value of the scan shows in cases where it changes the plan.

Age is also part of the decision. The Cochrane review states that with removals done at an older age, the risk of complications, pain and discomfort after surgery increases. This is not enough of a reason on its own to remove a tooth that causes no problems while you are young; but it is a factor to be taken into account when discussing with your dentist how likely the tooth is to cause problems over the years. If you have decided to keep the tooth, not skipping check-up appointments is part of that decision.

The first list gives situations suggesting the tooth can be monitored. If one of the findings in the second list is present, removal or another treatment comes into it; the examination and X-rays decide.

The order is first to rule out an emergency, then to understand whether the tooth is really causing a problem, and last of all to choose the method according to the nerve risk.

1. 1

   Ruling out emergency signs

   If there is difficulty breathing, speaking or swallowing, widespread swelling in the mouth, inability to open the mouth, swelling or pain in the eye or a sudden problem with vision, the assessment is done not at a dental surgery but at A&E; call 112. If there is swelling and a fever, see a dentist the same day.

2. 2

   Examination and questions about symptoms

   The dentist looks at whether the tooth opens into the mouth, whether there is inflammation under the gum flap, and whether there is decay or a pocket in the tooth in front of it. Say how many times you have had pain and swelling before and whether you have taken antibiotics; the number of pericoronitis episodes directly affects the decision.

3. 3

   Panoramic X-ray

   The position of the tooth, the shape of the root and its relationship with the nerve canal are assessed on a panoramic X-ray. Darkening of the root, interruption of the canal's white line or the canal changing direction shows an increased nerve risk.

4. 4

   A scan if needed

   If there is a risk sign on the panoramic X-ray, the dentist may ask for a scan to see the root's relationship with the nerve in three dimensions. This helps decide whether another method, such as coronectomy, should be chosen instead of full removal.

5. 5

   Choosing the method

   The options are monitoring, removing the tooth completely, or, if the nerve risk is high, removing only the crown and leaving the roots (coronectomy). Discuss in advance which method has been chosen and why, the nerve risk, and the fact that with coronectomy a second procedure may be needed later.

6. 6

   Removal

   According to the NHS, the gum is opened, some bone is removed if needed, the tooth is taken out in one piece or divided into pieces, and stitches are placed if needed. The procedure often takes a few minutes; according to the NHS, it is not expected to take more than 40 minutes, and most patients go home the same day.

7. 7

   Check-up

   The stitches and healing are checked. If the tooth has been kept, the check-up interval is set and the back surface of the tooth in front of it is assessed regularly.

There is no single right route with an impacted wisdom tooth. The choice is made according to the problem the tooth causes, how close it is to the nerve, and your preference.

The wrong decision can be made in either direction: unnecessary removal and making a problem tooth wait both carry a cost.

Healing varies with how deep the tooth was and how difficult the removal was. The sequence below is the usual course described by the NHS; your dentist's advice takes priority.

1. The day of removal

   The numbness lasts a few hours. There may be oozing from the extraction socket for a while; do not rinse your mouth vigorously, and to protect the clot, avoid strenuous exercise and smoking on the first day.

2. The next day

   According to the NHS, most people can return to their usual activities the next day. After a difficult removal or a general anaesthetic, 1–3 days off work may be needed.

3. The first two weeks

   Pain, swelling, bruising and stiffness in the jaw can last up to 2 weeks. During this time, soft foods and the painkiller your dentist recommends are usually enough.

4. Weeks and months

   If numbness has developed in the tongue, lip or chin, the NHS writes that it usually gets better but can last weeks or months. Going for regular check-ups during this period is important.

We do not give a figure here; the scope of removing an impacted tooth varies a great deal from tooth to tooth. The main factors that determine the scope:

How deep the tooth is and its position

A tooth lying on its side completely inside the bone needs longer surgery than a tooth that has partly opened into the mouth.

Imaging

Asking for a scan in addition to the panoramic X-ray changes the scope.

Method

Full removal or coronectomy; with coronectomy, a second procedure may be needed later.

Type of anaesthetic and number of teeth

Local anaesthetic, sedation or general anaesthetic, and how many teeth will be removed in the same session, determine the scope.