When teeth erupt (come through the gum into the mouth), they may twist, stick out, drop back, or overlap if there is not enough space in the mouth. Losing baby teeth early from tooth decay or trauma can lead to crowded permanent teeth. If crowded teeth affect a child’s self‐esteem or cause pain, damage or chewing problems, the child may be referred to a specialist dentist known as an orthodontist to correct them. Crowded teeth can be prevented or corrected using braces if crowding is mild (less than 4 mm). Removal of some teeth (extraction) may also be needed if crowding is moderate (4 to 8 mm) or severe (more than 8 mm). Fixed braces are used on permanent teeth. Removable braces can be used on baby or permanent teeth, or both. Baby or permanent teeth can be extracted.
What was the research?
A systematic review to evaluate scientific research on the effectiveness of orthodontic treatments (fixed braces, removable braces, tooth extraction) used to prevent or correct crowded teeth in children aged 16 years old or younger. We searched for studies that compared these treatments against no treatment, delayed treatment, placebo (pretend treatment) or another orthodontic treatment.
Who conducted the research?
The research was conducted by a team led by Sarah Turner of Liverpool University Dental Hospital, Liverpool, UK on behalf of Cochrane Oral Health. Jayne E. Harrison, Fyeza N.J. Sharif, Darren Owens and Declan T. Millett were also on the team.
What evidence was included in the review?
We included 24 randomised controlled trials that presented results from 1,314 children aged from 7 to 16 years in different countries. Twenty studies tested fixed braces, two tested removable braces and two tested extractions.
What did the evidence say?
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.
The Schwarz appliance is a type of removable brace which may reduce crowding in the lower arch when measured after nine months. Use of an eruption guidance appliance, for a year, may reduce the likelihood of crowding, but there may be other explanations for this. Again, we cannot be sure of these findings.
Taking out wisdom teeth does not seem to affect crowding later in life, while taking out the primary canine teeth 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.
How good was 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.
What are the implications for dentists and the general public?
Overall, the certainty of the evidence for the prevention and correction of crowding in children was very low, with many comparisons evaluated in single small studies, therefore the conclusions may not be generalisable, are subject to change with future research and should be interpreted with caution.
What should researchers look at in the future?
As the overall level of certainty of the evidence was very low, the results highlight the need for a systematic way of assessing, recording and measuring crowding in future research. This would allow comparison and combination of the results in meta‐analysis and provide a stronger level of evidence.
The results of this review show that there is a need for more long‐term, well‐designed and reported randomised controlled clinical trials to assess the preventive interventions and treatment options for crowded teeth in children. This is would be especially useful for interventions that are used in the primary and permanent teeth with the aim of preventing or reducing crowding in permanent teeth.
Link
Turner S, Harrison JE, Sharif FNJ, Owens D, Millett DT. Orthodontic treatment for crowded teeth in children. Cochrane Database of Systematic Reviews 2021, Issue 12. Art. No.: CD003453. DOI: 10.1002/14651858.CD003453.pub2.
This post is an extended version of the review’s plain language summary, compiled by Anne Littlewood at the Cochrane Oral Health Editorial Base.
Cochrane Oral Health 