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Crowding in the primary dentition. Cochrane Review 2021.

Crowding in the primary dentition

Dr. Michel Champagne, BA, DMD, MAGD, IBO, CDE  

Orthodontic treatment for crowded teeth in children (Review) Copyright © 2021.The Cochrane Collaboration. Published by John Wiley & Sons, Ltd.

What is a Cochrane Review and what is their reputation.

Cochrane (previously known as the Cochrane Collaboration) is a British international charitable organisation formed to organise medical research findings to facilitate evidence-based choices about health interventions involving health professionals, patients and policy makers. It includes 53 review groups that are based at research institutions worldwide. Cochrane has approximately 30,000 volunteer experts from around the world.

Cochrane has a very high reputation for its integrity and professionalism.

What were the main results?

Fixed braces and related items.

A lower lip bumper may prevent crowding when the adult teeth are starting to come through. Nickel-titanium wires may correct crowding better than wires made of copper nickel-titanium, and twisted multi-stranded (co-axial) nickel-titanium archwires may be better than single-stranded ones. However, we cannot be sure of these findings. For the other comparisons evaluated, it was not possible to show that one group did better or worse than the other for reducing crowding.

Removable braces and related items.

The Schwarz appliance may reduce crowding in the lower arch, when measured at nine months. Use of an eruption guidance appliance, for a year, may reduce likelihood of crowding, but there may be other explanations for this. Again, we cannot be sure of these findings.


Taking out wisdom teeth (third molars) does not seem to affect crowding later in life, while taking out the pointy baby teeth (canines) from the lower jaw, may reduce crowding in the short term, but we cannot be sure of this. There are probably other explanations for this finding.

What are the limitations of the evidence?

The evidence is uncertain. It consists of small, individual studies testing different treatments. Some of them have problems with how they were carried out. We cannot be sure about our findings and future research may change them.

How up to date is the evidence?

The evidence is up to date to January 2021.


Figure 1. Lower Schwarz

Figure 2. Lip bumper