Do wisdom teeth coming in cause tooth crowding? -

Teeth may shift over time but can this be caused by their third molars coming in? | What does dental research show? | How dentist's opinions about tooth crowding have changed with time.

Will having your wisdom teeth taken out prevent your other teeth from shifting?

The third molar / tooth crowding theory.

Some dentists hold the belief that as part of their normal eruption process a person's wisdom teeth direct pressure onto those in front of them as they come in. And as a result, these teeth become crooked (crowded).

Anterior tooth crowding after orthodontic treatment.

Lower incisor crowding that developed some years after orthodontic treatment.

Which teeth are usually affected?

The teeth most likely discussed or shifted are the lower front ones, especially the lower incisors (see picture). This phenomenon isn't usually a concern with upper teeth.

Clearly experiencing this problem would be a disappointment to anyone. But it is also of prime concern to orthodontists whose treatment is usually completed long before their patient's third molars have come in (usually ages 18 to 24). They refer to this type of relapse of their work as "secondary mandibular incisor crowding."

What if this theory is right?

Whether or not the tooth crowding / wisdom tooth theory is correct matters quite a bit ...

  • If it is, then most people who have wisdom teeth, at least lower ones, should have them removed as a preventive measure, so to reduce the risk of their teeth becoming crooked in the future.
  • Of course if it is wrong, then dentists would be recommending the removal of at least some people's third molars without merit because doing so would serve no purpose.

What does research show about the third molar / tooth crowding relationship?

You might be surprised to learn that the dental community at large has been investigating and debating this issue for over 100 years.

And while it seems that the majority of dentists, especially those trained more recently, now consider this theory to be invalid (an opinion that wisdom teeth do not cause tooth shifting and therefore should not be extracted as a preventive for it), it must be stated however that even today this controversy has still not been totally resolved.

How the opinion of dentists has changed over time.

As recently as 50 years ago (and possibly less, see below), a majority of dentists (specifically oral surgeons and orthodontists) felt that a correlation between wisdom tooth eruption and teeth shifting did exist.

A 1971 study reported that ...

  • 65% of orthodontists and oral surgeons support the idea that wisdom teeth produce an anteriorly directed force that causes the crowding of the mandibular incisors. (That's dental jargon for the problem we've stated above.)
  • And based on this opinion, they favored the removal of third molars to help prevent this shifting from occurring.

(Stanaityte 2014) [page references]

Choosing this stance was founded on research of the era.
  • A 1961 study by Bergstrom evaluated 60 patients who had congenitally missing (missing from birth) third molars on one side but not the other.

    It determined that a greater amount of tooth crowding existed in quadrants (for example the "lower left quadrant," which means all teeth on a person's lower left side) where wisdom teeth were present.

  • A study by Vego in 1962 came to the same conclusion after evaluating 65 patients, 25 of which had congenitally missing thirds.

(Antanas 2006, Almpani 2015)

Probably what was missing here was that each study only involved a small sample size. Also, possibly not enough research had yet been performed on this topic to develop a substantial conflicting or alternative view.

What has more recent research about wisdom teeth causing tooth crowding determined?

In the last 50 years quite a bit of additional research has been conducted on this subject. And it must be said that much of it is contradictory and/or inconclusive.

As a help in wading through and passing judgment on this data, we've decided to rely on the findings of several literature reviews that have already evaluated it. Their process typically involves:

  • Identifying relevant studies, evaluating their methods and looking for possible procedural inadequacies and biases, and then weeding out those that have obvious deficiencies.
  • Then from those that remain, evaluate their conclusions individually and then formulate a collective consensus about what they as a group have shown.

Literature reviews that have evaluated the wisdom teeth / teeth crowding theory.

#1- Costa (2013)

The primary goal of this review was to see if evidence could be found that supported the prophylactic (preventive) removal of wisdom teeth in general. It evaluated 260 papers. Only two of these met their screening criteria and also addressed the topic of tooth crowding.

The opinion drawn was that the only scientific proof available suggests that the prophylactic extraction of wisdom teeth for the purpose of preventing the shifting of the lower incisors is not justified.

#2- Stanaityte 2014

This paper evaluated 223 articles, of which only 21 met its screening criteria. The authors readily stated that collectively they were quite contradictory and supported both sides of the teeth-shifting argument.

They concluded that "third molars do not cause tooth crowding." But did state that they may play some role in combination with other factors (see below). However, this review did not make a recommendation for the prophylactic removal of wisdom teeth.

#3- Almpani (2015)

This review pointed out that the insufficiency of high-quality studies makes it difficult to formulate definitive guidelines. But stated that there is currently "no sound research evidence supporting the prophylactic removal of non-pathological impacted third molars."

What's interesting is what the authors of this paper noticed a transition in opinion of researchers over the decades.

  • Studies conducted in the 60, 70 and 80's seemed be more likely to associated the occurrence of tooth shifting with the presence of wisdom teeth.
  • In contrast, from the 1990's forward study findings tend to exculpate third molars in this matter and generally characterize their removal as a preventive measure as unjustifiable.

What is the current opinion of dentists on the wisdom teeth / teeth shifting debate?

We found a study that seems to confirm the change in attitude that the Almpani paper just discussed suggests. In contrast to the statistics cited above for the 1970's era, the current opinion of clinicians is apparently different now.

Study: Current attitudes of dentists about tooth crowding caused by wisdom teeth.

Lindauer (2007) surveyed roughly 400 orthodontists and oral surgeons (for a total of over 800 clinicians) in regard to the theory: Do erupting wisdom teeth cause anterior tooth crowding? The findings of the study were:

  • At 57%, oral surgeons (clinicians whose business is performing extractions) were more likely to "generally" or "sometimes" recommend the prophylactic removal of 3rd molars to prevent tooth shifting.
  • In comparison, 64% of orthodontists stated they "rarely" or "never" recommend it.

    [If extracting third molars reduced the potential for tooth shifting, orthodontists would have fewer case failures (relapse) over time. So their lack of support for this theory is telling.]

The age of the clinician seems to be a factor in which opinion they hold.

The author noticed a relationship between the age (year graduated) of the clinician and their response.

  • More recently graduated orthodontists were less likely to favor removal.
  • Oral surgeons that were further along in their careers (had graduated in the 1970's or 80's) were more likely to recommend wisdom tooth removal.

These findings suggest that the developing trend in opinion of clinicians is that removing wisdom teeth doesn't play a significant role in preventing tooth crowding and is therefore unwarranted.


Other theories used to explain tooth crowding.

Nothing on this page is meant to suggest that people who have third molars don't have teeth that do shift during their lifetime. But rather that research has not been able to definitively demonstrate a firm statistical correlation between the two.

That's lead some researchers to suggest other reasons as a cause of this phenomenon. Some of them are:

  • Due to normal biological processes (such as bone remodeling) the precise size and shape of a person's jawbone tends to change over time.

    In regions where the dimensions of the jawbone may become reduced (like the area between the lower eyeteeth), since the available space is now less but the size of the teeth remains the same, there's no way for tooth crowding not to result.

  • Dental factors that may be involved include the position of the permanent tooth buds (the tissues from which teeth form), the timing of deciduous (baby) tooth loss and permanent tooth eruption, the effect of pressure generated by soft tissues (lips, tongue, cheeks) and the positioning of the opposing (opposite) teeth.

If you're interested in more detailed information, our references page contains a link to Karasawa 2013. Its discussion outlines the topic of tooth crowding fairly extensively.


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