What does the science say?
The issue of wisdom teeth and congestion has been the subject of a number of high-profile studies over the past 50 years, using different methodologies. The scientific consensus is not based on a single study but on prospective cohort studies and randomised controlled trials (RCTs).
Here are the main types of research, with specific data:
The Bergström and Jensen study (Classic control group)
It is one of the most cited studies that laid the foundations the position today.
Measurement method: Patients were studied who were missing wisdom teeth on one side (either due to germ deficiency or premature extraction) and had them on the other side.
Sample: Long-term (years) follow-up of dozens of patients.
Result: The researchers found that the degree of dental crowding was statistically the same on both the wisdom tooth and the non-wisdom tooth sides.
CONCLUSIONS: If the wisdom tooth were the main cause, the congestion should only occur on one side.
Prospective longitudinal studies (The time factor)
In the 1980s and 1990s, several universities (e.g. Lund University in Sweden) followed the same subjects for decades.
Measurement method: Plaster samples and X-rays (panoramic and teleradiographs) were used to measure the length of the dental arch and the inclination of the teeth.
Result: It was found that crowding of the front teeth (an average of 1.5-2 mm narrowing between canines) occurred in everyone, regardless of their wisdom teeth:
- They have broken perfectly.
- They remain in retention (under the gums).
- Or they were missing in the first place.
The Cochrane Review (The pinnacle of evidence)
The Cochrane Collaboration is the world's most prestigious medical summarisation organisation.A meta-analysis was conducted in 2012 (and updated later).
Measurement method: Only the most rigorous randomised controlled trials (RCTs) were considered.
Sample: Data from hundreds of patients were pooled, with one group of participants having their wisdom teeth extracted preventively and another not.
Result: They found insufficient evidence that the removal of wisdom teeth prevents later congestion. The difference between the two groups (extracted vs. not extracted) was less than 0.2 mm, which is clinically insignificant.
Why did they used to believe the opposite?
(The correlation vs causality fallacy) The misunderstanding is due to statistical coincidence:
- Wisdom teeth usually try to emerge between the ages of 17 and 25.
- The crowding of the lower incisors also becomes visible between the ages of 17 and 25 (due to the late growth phase of the jaw).
Since the two events happened at the same time, doctors assumed that one was the cause of the other. But modern 3D imaging and biomechanical modelling have shown that the wisdom tooth pressure is „absorbed” at the contact points of the grinding teeth, and does not reach the front teeth with enough force to move them.
If it is not the wisdom tooth, what exactly are the biomechanical forces (e.g. lip pressure, chewing force) that cause congestion?
Wisdom teeth are therefore exempt, but congestion is still a reality. Biomechanics and dentofacial orthopaedics identify three main culprits, the most exciting of which is the ongoing „battle” between the jaw and the soft tissues.
A MANDIBULA (jaw) „LATE” GROWTH: Although our body height remains constant, the bone structure of the jaw undergoes microscopic changes until the early twenties (sometimes even longer).
DIFFERENTIAL GROWTH: The lower jaw (mandible) often grows a little further or at a different rate than the upper jaw (maxilla). As the lower jaw moves forward, the lower incisors „bump” into the inner surface of the upper teeth.
THE „MELODY EFFECT”: As the upper teeth block the progress of the lower teeth, the lower incisors have nowhere to expand, so they start to fall in behind each other, crowding in.
A PHYSIOLOGICAL SPECIALISATION (The „migratory tendency”): Teeth are not static objects in the bone. They have a genetically encoded and biomechanically maintained tendency to move towards the midline.
ABRASION ABRASION (Interproximal abrasion): during evolution, chewing wears down the contacting lateral surfaces of teeth. As the teeth narrow, the force of the chewing muscles and the fibres of the tooth socket constantly push them forward to close the gaps.
VECTOR: This continuous forward force (mesialisation) is concentrated at the front teeth. Because canines are more stable, the smaller incisors between them give up the fight first and slide over each other.
LIP PRESSURE AND THE „SOFT TISSUE CURTAIN” (Soft tissue curtain): teeth are located in a neutral zone: on the inside, they are pushed outwards by the tongue, and on the outside, they are pushed inwards by the muscles of the lips and cheeks.
CHANGES IN MUSCLE TONE: As we age, the lips become firmer and the skin and connective tissue become less elastic, often resulting in increased inward pressure on the lower lip.
A SATUE EFFECT: If the lip pressure overcomes the force of the tongue, the circumference of the dental arch begins to slightly narrow. Since the size of the teeth (mesiodistal width) does not change, they can only fit in the smaller circumference in a congested way.
Why is this clinically important?
This realisation fundamentally changed orthodontics.
Retention lasts forever: It used to be thought that once the growth was complete and the wisdom teeth were out, the teeth would stay in place. We now know that because of these forces, lifelong retention (fixed wire or night splint) is required for stability after orthodontic treatment.
Wisdom tooth surgery is not prevention: You shouldn't have a healthy wisdom tooth removed just to „see if it will warp your bottom line” - because research shows that there is a good chance that crowding will still occur after surgery.
How does modern orthodontics compensate for these natural forces (e.g. with IPR - interproximal reduction)?
Since modern orthodontics no longer sees wisdom teeth as the main enemy, but the natural narrowing of the perimeter of the dental arch, the strategies for solving the problem have also changed. The goal is no longer „to make the space at any cost” (e.g. to extract healthy small molars), but to achieve biomechanical balance.
One of the most important tools is IPR (Interproximal Reduction), but let's look at the full toolbox:
- IPR (Interproximal Reduction / Stripping)
IPR means minimal, precision grinding of the lateral surface of the tooth. It is a technique that simulates natural wear (which would have been done by our ancestors chewing) using modern tools.
How it works: A special ultra-thin diamond-coated strip or disc is used to remove 0.1-0.5 mm of enamel per tooth at the interface.
The biomechanical advantage of gaining space: If you do 0.2 mm IPR on 10 teeth, you have already gained 2 mm in the dental arch, which is often enough to unblock the congestion.
Stability: The point of contact of the teeth becomes a wider „surface”. Flatter surfaces are more difficult to slide past each other under mesialisation pressure than point contacts.
Aesthetics: Eliminates the „black triangles” (gum deficiency) between crowded teeth.
- Arch Expansion (Arch Expansion)
Rather than pulling teeth out, modern appliances (especially Invisalign-type splints and self-ligating braces) can expand the arch laterally.
A mechanism: Teeth are not only deciduous, but the entire root is gently pushed outwards in the bone (biological limits permitting).
Risk: This is where the lip pressure mentioned earlier comes in. If you expand the gum too wide, the muscles of the lips („soft tissue curtain”) will push the teeth back after treatment. Therefore, it is important to know the limits.
- The modern rhetoric: „Forever” stability
Since research has shown that the forces that cause congestion (lip pressure, jaw growth) are present for the rest of our lives, orthodontic treatment no longer ends with the removal of the appliance.
Fixed Retainer (Fixed retainer): A thin wire glued to the inner surface of the front teeth. This prevents the incisors from rotating or sliding on top of each other due to mesialisation pressure.
Vivera / Night rails: They preserve the full form of the conceptual arch.
In summary:
The question of wisdom teeth is now more scientifically clear than ever. The available research suggests that they are not responsible for the crowding of the lower front teeth - the real causes are much more complex and lie in the late growth of the jaw, physiological mesialisation and the ongoing muscular imbalance of the soft tissues.
This change in attitude has fundamentally reshaped modern orthodontics: the emphasis is no longer on removing the „scapegoat”, but on understanding biomechanical balance, long-term stability and conscious retention.
If you found the topic interesting and would like to understand the science and biomechanics behind orthodontics in more depth, read more articles on the blog or contact us for a consultation.
