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Wisdom teeth – Myths and realities

Wisdom teeth – Myths and realities

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Should they be removed? When and why?

 

We can have up to 32 teeth in the mouth including wisdom teeth (*), but it is very rare to see a dentition with all the teeth positioned in an esthetic and functional way, as in this case. (This dentition was treated orthodontically.)

Wisdom teeth are time bombs
But what about impacted teeth that are asymptomatic? Wisdom teeth have historically been blamed for many problems. They are accused, among other things, to cause tooth movement by exerting pressure on other teeth when trying to erupt. This would be responsible for the movement of other teeth and the increase in dental crowding and rotation of the anterior teeth with time. Is this “popular belief” justified?

 

Examples of impacted third molars that can only be seen with the help of radiographs.

There are, however, several other reasons to extract third molars.

Although both wisdom teeth came out, they are partially covered with gum tissue and difficult to clean. They have become decayed within only a few months

Although both lower third molars of this 24-year-old woman are partially erupted, they are partially covered with gum tissue (semi-impacted) and difficult to clean. They have become decayed within only a few months of their eruption (arrows and dark areas on X-rays show decay). It is preferable to extract these third molars before the problem worsens.

However, if you prefer to keep asymptomatic impacted wisdom teeth, do not ignore them.

Note that it is rarely necessary to extract third molars as part of an orthodontic treatment. However this may be necessary if, for example, those teeth would interfere with the normal eruption of another molar (second molar) or prevent the movement of teeth towards the back of the mouth. Another exception would be when a jaw surgery, such as a mandibular advancement, is planned (orthognathic surgery). In such a case, the oral surgeon will prefer to extract the lower wisdom teeth at least six months prior to the surgery in order to avoid a “bad split” of the mandible during the surgical intervention.

We like to use the “jack-in-the-box” analogy to try to describe certain unpredictable dentition problems and behaviors. Wisdom teeth are well suited for this comparison; it is hard to predict if they will come out and if so, how and when. They are full of surprises!

 

Examples of third molar eruption problems

Impacted upper and lower third molars leaning against the second molars in a 21-year-old male.

Impacted upper and lower third molars leaning against the second molars in a 21-year-old male. There are even 2 upper wisdom teeth on the right radiograph! These molars will not erupt and can damage other teeth.

Examples of impacted wisdom teeth (third molars) located under the second molars that started to resorb the roots to such an extent that second and third molars had to be extracted.

Impacted wisdom teeth (upper and lower third molars) located under the second molars that started to resorb the roots of the second molars to such an extent that both third AND second molars had to be extracted. (courtesy of Dr G. Noreau)

Upper third molar eruption problems. Only a radiograph can detect this anomaly (25-year-old woman).

Upper third molar eruption problems. Only a radiograph can detect this anomaly (25-year-old woman). These teeth will not erupt adequately and their extreme malposition justifies their extraction. The tooth on the picture on the right can damage the second molar if it stays in the mouth.

A routine radiograph in this 13-year-old patient reveals impacted lower wisdom teeth that are almost not formed but overlap the roots of the second molars, which could damage them in the long term. It would be indicated to extract them before the formation of their roots is too advanced. Note that such situation can be asymptomatic for the patient.

Predicting the eruption of wisdom teeth

 

Look at the following examples of radiographs that show the behavior of wisdom teeth over many years.

Who could have predicted what happened?

Note: The letters represent the patient’s initials and the numbers are the patient’s age at the time the radiographs were taken.

Wisdom teeth orthodontist Lemay FC 971175

Wisdom teeth third molars orthodontist Lemay JH

Wisdom teeth orthodontist Lemay VL AC

Wisdom teeth third molars orthodontics Lemay SP

Eruption of a wisdom tooth that migrated forward.

(A) A wisdom tooth was visible on a radiograph, far behind the second premolar as early as 11 years of age. (B) 3 years later, this tooth seems farther away. (C) After a few years, the impacted molar migrated forward and seems to be on the right path to erupt. Who could have guessed? To be continued…

 

Change in the position of wisdom teeth from age 15 to 21

Evolution of the position of lower wisdom teeth during a 6-year period. As soon as the teeth will obviously not come out properly, it would be preferable to extract them to avoid a more complex intervention (extraction) later on (for the patient and the surgeon).

Evolution of the position of lower wisdom teeth during a 6-year period. As soon as the teeth will obviously not come out properly, it would be preferable to extract them to avoid a more complex intervention (extraction) later on (for the patient and the surgeon).

 

Other considerations in the decision to remove or retain third molars

Absence of opposing teeth

It is indicated to extract wisdom teeth that have no opposing tooth (*) in the lower arch, even if they erupt.

 

When a tooth is partially out, the gingiva covering it is an area where plaque and food debris can accumulate and cause infection, inflammation and tooth decay. It is then indicated to either uncover such a tooth by removing the excess gum tissue or to extract it if the tooth cannot be properly uncovered to help it complete its eruption.

A semi-impacted third molar is more difficult to clean which makes it more susceptible to dental caries. This tooth shows an incipient carious lesion in the surface groove.

Misleading images!

Sometimes, the clinical examination gives the impression that the eruption of wisdom teeth occurs well or normally, but the radiological examination reveals a whole different reality.

Horizontal semi-impacted wisdom tooth

Presence of damaged teeth

When a wisdom tooth has little chance of coming out and another tooth in front of it is severely damaged to the point where major restorations will be necessary later on, it could be logical to extract the damaged tooth and “recuperate” the wisdom tooth. In such a situation, it is beneficial to postpone the decision to extract a third molar if an orthodontic treatment is envisioned. Extracting the wisdom tooth would force the patient to restore the damaged tooth or replace it if it were to be extracted eventually.

Extraction of a molar and recuperation of the wisdom tooth in orthodontics

Not having extracted an impacted wisdom tooth very early made it possible to recuperate it and eliminate a severely damaged molar.

(A and C) 15-year-old teenager with a lower left molar (black * asterisk) that is severely compromised by a root canal treatment. Extracting this molar made it possible to recuperate the impacted and tipped wisdom tooth (red *) and close the space remaining following the extraction by moving the other molars forward (arrow).
(B and D) After the corrections, the space created by the extraction is completely closed, the wisdom tooth (third molar) came out, uprighted and is now functional. The green asterisk (*) indicates where the wisdom tooth was.
This patient thus avoided the necessity to have a crown which, since he was very young, would have required to be replaced several times throughout his life.


Do all third molars need to be extracted?

Sometimes, a single wisdom tooth seems problematic and must be extracted. What about the other third molars that stay in the mouth? Should they necessarily be extracted as well? To learn more about it, consult our Ortho-blog column “Do all third molars need to be extracted?” describing certain points to take into consideration to decide which wisdom teeth need to be extracted. Dental supra-eruption of a wisdom tooth
Temporomandibular joint disorders involve several factors

The behavior of wisdom teeth is hard to predict. It answers a very complex “equation” with several variables. Each of them can influence individually or together the symptoms and evolution of the eruption of teeth.

Lack of symptoms doesn’t mean lack of disease

The influence of wisdom teeth on stability of teeth


References:

1- White RP, Proffit WR – Am J Orthod Dentofac Orthop 140:10-16, 2011.

 

  Dernière mise-à-jour : 2017-01-03 à 16:59:01 © Jules E. Lemay, www.ortholemay.com – Tous droits réservés / All rights reserved

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