Once people finish having their teeth straightened with orthodontic braces, the teeth will tend to get crooked again. Orthodontists try to prevent this by using different retention procedures. Retention procedures can include either wearing retainers, which fit over or around teeth, or stick onto the back of teeth, or by using something called ‘adjunctive procedures’. Adjunctive procedures either change the shape of the contacts between teeth, or involve a very small procedure to cut the connection between the gum and the neck of the tooth. This is an update of a Cochrane review published previously in 2006.
What was the research?
A systematic review of the evidence to find out which approach is most effective at maintaining teeth in their new position after the end of treatment with orthodontic braces
Who conducted the research?
The research was conducted by a team led by Simon Littlewood from St Luke’s Hospital Orthodontic Department, Bradford, on behalf of the Cochrane Oral Health Group. Declan T. Millett, Bridget Doubleday, David R. Bearn and Helen V. Worthington were also on the team.
What evidence was included in the review?
Data was extracted from 15 randomised controlled trials, which looked at different types of fixed and removable retainers and different durations of wear. There were 1,722 participants in the trials, including adults and children. Nine studies took place in a hospital or university setting, five studies in specialist practice and one in a National Health Service Clinic. The trials evaluated four comparisons: removable retainers versus fixed retainers (three studies); different types of fixed retainers (four studies); different types of removable retainers (eight studies); and one study compared a combination of removable and fixed retainers, use of an adjunctive procedure and a positioner.
What did the evidence say?
Most of the evidence was of low quality. One small but well conducted study that compared full-time and part-time wear of thermoplastic retainers did not find evidence of a difference in stability (moderate quality evidence).
How good was the evidence?
There is not enough high quality evidence to recommend any one approach to retention over another. Further high-quality studies are needed.
What are the implications for dentists, orthodontists and the general public?
No evidence was found that wearing thermoplastic retainers full-time provides greater stability than wearing them part-time, but this was assessed in only a small number of participants. Overall, there is insufficient high quality evidence to make recommendations on retention procedures for stabilising tooth position after treatment with orthodontic braces. Further high quality trials are needed.
What should researchers look at in the future?
Retention studies are not easy to undertake, but several randomised controlled clinical trials have now been completed showing that this research is possible. Relapse is a long-term problem and long-term follow-up of participants is practically difficult and can be expensive. However, given that the vast majority of people requiring orthodontic treatment undergo a phase of retention, this vital area of orthodontic research should continue to be given priority. Further trials should be done to compare different types of retainers, the effects of different adjunctive techniques and whether they can be undertaken without retainers. Patient satisfaction should be a particular concern. Trials should ideally be followed up for a number of years.
Littlewood SJ, Millett DT, Doubleday B, Bearn DR, Worthington HV. Retention procedures for stabilising tooth position after treatment with orthodontic braces. Cochrane Database of Systematic Reviews 2016, Issue 1. Art. No.: CD002283. DOI: 10.1002/14651858.CD002283.pub4.
This is an extended version of the review’s plain language summary, compiled by Anne Littlewood at the Cochrane Oral Health Group Editorial Base.