Direct answer
Not always. A third molar — also commonly known as a wisdom tooth — that is well positioned, functional and can be kept clean does not need to be extracted. Extraction is, however, indicated when there is pain, infection, damage to the neighbouring tooth or a cyst, or when its position makes it foreseeable that such problems will arise. The decision is an individual one and is taken on the basis of a clinical assessment and a three-dimensional study — cone beam computed tomography, or CBCT, also commonly known as a 3D X-ray or CT scan.
Wisdom teeth, or third molars, are the last teeth to come through, usually between the ages of 17 and 25. When there is not enough space in the arch, they remain retained — wholly or partly — within the bone or beneath the gum. That is what is known as retention or impaction.
An impacted wisdom tooth may stay in the mouth for years without causing any symptoms. The absence of symptoms does not, however, mean the absence of a problem: over time, that same tooth may cause repeated infections of the gum covering it, decay on the back surface of the tooth immediately in front — the second molar —, resorption of the root of that tooth, or give rise to a cyst.
The most common indications for the removal of these teeth are:
Outside these situations, an asymptomatic wisdom tooth that can be kept clean may be monitored. Extracting for the sake of extracting is not a neutral decision: it is surgery, and all surgery carries risks. Nor is monitoring: the decision — to extract or to keep under observation — calls for a rigorous clinical assessment, case by case.
In lower wisdom teeth, the roots may lie very close to — or in contact with — the canal carrying the inferior alveolar nerve, which is responsible for sensation in the lower lip, the chin and the teeth of that quadrant. That is why these operations call for careful prior study.
The panoramic radiograph shows the proximity, but it is a two-dimensional image. When there are signs of an intimate relationship, use is made of cone beam computed tomography — CBCT, also commonly known as a 3D X-ray or CT scan, which makes it possible to see the exact position of the canal in relation to the roots — whether it lies buccally, lingually or between them — and to plan the surgery accordingly.
It is worth saying this clearly: removing an impacted wisdom tooth is not comparable to extracting an ordinary tooth. It is surgery of a higher degree of complexity, and that degree varies from case to case — it depends on the position and the inclination of the tooth, on the depth of the impaction, on the shape of the roots and on their relationship with the nerve.
Everything else follows from that. From the assessment of the impaction come the decision to extract or to monitor, the surgical approach to be followed, the information the patient has to receive before consenting — what is going to be done and what risks exist in their particular case — and the postoperative care they will be advised to take. Treating this surgery as a routine extraction is, in itself, an added risk.
In cases of close proximity to the nerve, there is an alternative to complete extraction: removing only the crown of the tooth and leaving the roots in place, without mobilising them. It is called a coronectomy.
The evidence is consistent as to its benefit in these selected cases. A meta-analysis of 34 studies, with 7,115 wisdom teeth in 4,477 patients, found a substantially lower risk of inferior alveolar nerve injury with coronectomy than with complete extraction (RR 0.1; 95% CI: 0.0–0.2), as well as a lower risk of lingual nerve injury and of dry socket [2]. A second meta-analysis, with 42 studies and 3,095 patients, reached a concordant result (OR 0.14; 95% CI: 0.06–0.30) [3].
It has, however, a cost that should be stated with the same clarity: the roots left behind migrate over time, and a proportion of cases need a second procedure. In the most recent meta-analysis, reintervention occurred in 3.63% of cases, exposure of the roots in 2.66% and failure of the technique in 2.79% [2]; in another, the risk of reintervention was about five times higher than that of extraction [3].
Coronectomy is not, therefore, a better technique than extraction: it is the technique indicated in a subgroup of cases, in which a permanent neurological risk is traded for a probability of a second operation.
It is carried out under local anaesthesia, and may be combined with sedation. The access is planned beforehand on the imaging, and the aim is to remove the tooth with the most contained intervention possible on the bone and the soft tissues.
Postoperatively, swelling, some discomfort and limited mouth opening are to be expected, more marked in the first 48 to 72 hours and subsiding over the course of the first week.
A note on the evidence for the techniques
The Cochrane review that compared surgical techniques for the removal of lower wisdom teeth included 62 randomised trials and 4,643 participants and concluded that, for most of the comparisons — flap design, method of bone removal, irrigation, type of closure —, the certainty of the evidence is low or very low, which does not allow one technique to be recommended over the others [1]. This means that the choice of technique rests on the judgement and the experience of the surgeon, and that it is reasonable to be wary of anyone who presents a method as proven to be superior.
When to make contact after the surgery
Pain that increases from the third day onwards instead of decreasing, fever, increasing swelling, progressive difficulty in opening the mouth, a persistent taste of infection, bleeding that does not stop with pressure, or altered sensation in the lip or the tongue that persists beyond the effect of the anaesthetic.
References
References retrieved via PubMed.
Related questions
The assessment starts with establishing whether there is an indication to extract — and, if there is, which approach carries the lowest risk in your case.
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