Do all wisdom teeth need to be extracted?

People often ask us if, when it is indicated to extract a wisdom tooth for some reason, it is also indicated or essential to extract the other wisdom teeth that can be present in the mouth or visible on radiographs.

The same conditions and reasons described in our section on wisdom teeth apply to all third molars when it comes to deciding if they need to be extracted. Consult the section on wisdom teeth to learn more on this subject. However, we now bring precisions on the impact that the extraction of only one wisdom tooth may have on the dentition and occlusion.

Loss of a tooth = occlusal imbalance

• It is often indicated to extract more than one if not all wisdom teeth. However, a particular situation exists when only one wisdom tooth must be extracted; the opposing tooth ends up without support and can therefore continue its eruption process and create other problems.
• Teeth are subjected to several forces that act in the mouth; mastication, perioral musculature (tongue, cheeks, lip), habits (finger sucking), etc., but all these forces are normally in balance for the dentition and occlusion to be stable.
• With a normal dentition and occlusion, well-aligned teeth have a certain “interdigitation” that allows the opposing teeth to distribute the functional and masticating forces optimally. When this balance is disturbed by the extraction or the loss of a tooth, this results in an imbalance in the forces and the opposing tooth (in the other dental arch) can tend to “lengthen” downward (for an upper tooth) or “go up” for a lower tooth.
• Everything that can disturb the stability of the dentition can potentially modify the balance in the forces and influence the position of teeth. Thus, the opposing teeth (in each arch) “support” each other mutually in function by opposing the forces generated. The molars can support forces up to 120 kg!
• If a tooth is extracted and therefore no longer supports the opposing tooth, the opposing tooth will tend to continue its eruption until it finds new support to stop it.
• The same concept applies to a wisdom tooth that comes out and that does not have any opposing tooth. Sometimes the tongue interposes itself in the free toothless space and can serve as “support” to the erupting tooth and prevents or minimizes its vertical movement, but this is hard to predict. A tooth that erupts that way can be monitored for a while before making the decision to extract it and if it becomes symptomatic, if it migrates, or causes other problems, it will always be possible to extract it.
• This phenomenon also applies to the other teeth as well, not only to wisdom teeth, because the same forces and principles are involved.

With a normal dentition and occlusion, interdigitation of teeth allows them to function and support each other well.

Not only wisdom teeth

• The situation described previously can occur with any tooth and not only with wisdom teeth. A tooth that does not have any support in the opposing arch will not be stable over time.
• If a wisdom tooth is involved, it is often indicated to extract it before it starts moving vertically, but if another tooth is involved, it is preferable to replace the missing tooth to restore the balance that existed before the extraction or the loss of this tooth. This requires a prosthetic replacement, such as a dental implant, a fixed bridge, a removable partial prosthesis or any other means suggested by the general dentist.
• A temporary alternative is to immobilize the tooth without support to prevent its migration. This can be indicated for a tooth that is not a wisdom tooth before the opposing tooth can be replaced. In the case of a wisdom tooth, this solution is not really useful, because it is not logical to replace a missing wisdom tooth by a prosthesis (in the case of a complete and normal dentition).

If there is the slightest contact or support between a third molar that is fully erupted and cleared and an opposing tooth, its extraction or immobilization should not be necessary and this tooth could be preserved if there are no interferences with other teeth during its function. The vertical contact between both teeth should be enough to stabilize the two opposing teeth.

Examples of excessive eruption following the loss of teeth. This phenomenon can take several years to occur.

(A) Excessive eruption of upper teeth that are no longer supported following the loss of lower molars. (B) Open mouth: the teeth are so far down that they touch the lower gum tissue (circle). (C) In addition to lengthening downward, the affected molars are tipped inward.

Loss of posterior teeth in an adult. On one side (A), the loss of a lower molar allowed the other molars to tip forward. On each side (A and B), the upper molars migrate toward the lower space (extrusion). These teeth will ideally have to be repositioned to allow the dentist to perform a better prosthetic replacement of the missing teeth.

Example of extreme vertical movement of posterior teeth several decades after the extraction of opposing teeth and the lack of replacement of teeth by a dental prosthesis. (A, C) The premolars and a molar were extracted on each side in the upper arch, as well as the lower molars. Over the years, the lower premolars migrated upward while the upper molar “got longer”. (B) Front view. A prosthetic replacement of the missing teeth would have prevented these changes in the position of teeth that no longer had opposing teeth in the other arch. Orthodontic corrections are now a lot more complicated!

Examples of indications to extract in the opposing arch

In the example on the opposite side, a 17-year-old young man, not having had any orthodontic treatment, has his 32 teeth in the mouth (including the wisdom teeth). Despite certain irregularities in the occlusion and alignment of teeth, all his third molars are functional. However, the one on the lower right side (*) shows decay. This tooth being in function with the one in the upper arch, if the cavity is not too big, it could be eliminated and the tooth could stay in the mouth. However, if the cavity was major to the point where a large obturation, a root canal treatment, a crown, etc. would be necessary, it is therefore more logical to extract the affected tooth. This would then create the situation described previously where the opposing wisdom tooth would no longer be supported and would get longer over time. It would thus be also indicated to extract it. This example illustrates how a healthy and previously functional tooth (the upper left third molar) must be extracted following the loss of an opposing lower wisdom tooth.

This adult’s lower wisdom teeth will not erupt since his growth is completed. It is indicated to extract them. The upper right wisdom tooth is already starting to lengthen (yellow arrow). The left one can continue its eruption over the years but, if it comes through the gum tissue, it will not have any opposing teeth and it will be indicated to extract it as well. It can also be extracted now, but waiting a while will allow it to come down a little bit more and the extraction will be easier for both the patient and the dentist.

A particular situation

Each case is unique and should be evaluated as such. In the following example, the lower wisdom teeth must be extracted for obvious reasons; they are semi-impacted and in a horizontal position (blue and black * in A and B).

– The lower left wisdom tooth erupts in the mouth (arrow in D), but will never erupt completely.
– In the upper arch, the upper right first molar (yellow * in A and C) must be extracted because it is fractured and cannot be saved (yellow X in A and C).
– Normally, the extraction of the upper wisdom teeth would also be recommended (green and red * in A, B and C), because they would not have any opposing teeth but, since the damaged molar must be extracted, it was recommended to keep the upper right third molar (green *) and move both molars forward (red arrows). This makes it possible to close the space left behind by the extracted tooth and preserve the wisdom tooth.
– On the left side, the wisdom tooth must be extracted (red *), because it is “getting longer” in the absence of opposing contact.

The lower wisdom teeth must be extracted, but an upper wisdom tooth can be preserved because it will be moved forward orthodontically.

➡ To learn more on wisdom teeth.