At a glance
After orthodontic treatment, teeth tend to move back towards where they started; a retainer, either a wire bonded behind the teeth or a removable tray, holds them in place. No study sets a length that suits everyone, and teeth can keep moving years later. So a retainer is worn for a long time, as your dentist advises.
Why do teeth move after treatment?
A tooth is not cemented into the bone: fibres hold it there, which is what allows it to be moved. Once treatment ends, those fibres and the gum keep a trace of the old position for a while. Without a retainer, teeth tend to go back to it: this is called relapse.
The other reason is time. In 31 patients re-examined 10 and then 20 years after their retention ended, crowding of the lower front teeth kept increasing, more slowly after 10 years, and alignment was still judged acceptable in only 10% of cases. Their treatment, decades ago, had included extractions: a signal to take seriously, not a forecast for you.
In other words, part of the movement is a return towards the old position, and part comes from the mouth itself, which keeps changing with age. A retainer helps in both cases.
Bonded wire or retainer tray: which retainer?
There are two main kinds of retainer, often used together:
- the bonded wire, or fixed retainer: a thin wire glued behind the front teeth, hidden from the front, working day and night with nothing for you to do;
- the retainer tray, or removable retainer: a clear tray much like an aligner, worn as prescribed and taken out to eat.
| Criterion | Bonded wire | Retainer tray |
|---|---|---|
| Visibility | Hidden behind the teeth | Clear, hard to notice once in |
| Effort | Nothing to put in or take out | To remember every night, or day and night at first |
| Cleaning | Small brush or floss under the wire, daily | Tray cleaned separately, usual brushing |
| What can go wrong | Coming unstuck, sometimes unnoticed | Lost, broken or worn |
| Check-ups | Bond checked at visits | Fit checked at visits |
Why both together? The wire holds the front teeth all the time, the ones most inclined to move; the tray holds the whole arch, back teeth included. And if the wire comes loose without you noticing, the tray keeps holding the teeth until your next appointment.
What do studies say? For retention after a fixed appliance, they find few differences in stability between retainer types. Worn part-time, a tray leaves slightly more relapse than a bonded wire, with no clinically important gap; it has fewer mishaps (broken, lost, worn out or no longer fitting), is less comfortable, and gums are healthier. Worn full-time, on the other hand, a tray has more mishaps than the wire, again with healthier gums. These results remain weak: no type of retainer suits everyone.
How long do you need to wear a retainer?
There is no proven length that suits everyone. The evidence cannot settle which method is better, and most studies measure results at under a year.
What is known is that teeth can keep moving for years after treatment ends. That is why a retainer is worn for a long time: often day and night at first, then at night.
Do you need a retainer after clear aligners?
Yes. Teeth moved by trays follow the same rules as teeth moved by a fixed appliance, so supervised retention is recommended for every patient, aligner patients included. The results above on retainer types, however, come from treatment with fixed appliances, not aligners.
A retainer tray looks like an aligner, but it moves nothing: it holds. You keep it, whereas an aligner is changed every 10 to 15 days. The full course of treatment is described on the clear aligners page.
How do you look after a retainer day to day?
- brush the tray in cold or lukewarm water, without abrasive toothpaste, and always keep it in its case;
- avoid hot water, which can warp it;
- around a bonded wire, use a small interdental brush or floss with a threader every day: plaque builds up there easily;
- avoid biting very hard food with your front teeth (stones, bones, hard nuts), which can loosen the wire;
- bring your retainer tray to every check-up.
What if the wire comes loose or the tray breaks?
Do not leave it. A loose wire no longer holds the teeth it covers, and a broken or lost tray holds nothing at all. Teeth can then start to move.
- Let the practice know and book an appointment.
- If you also have a retainer tray that still fits well, wear it until the appointment.
- Do not glue the wire back yourself or cut off a piece that pokes: cover it with orthodontic wax.
- If the tray no longer goes in without forcing, do not force it: your teeth may already have moved, and it is for your dentist to assess what comes next.
If your teeth have already started to move, the guide to teeth that move after orthodontic treatment explains what can be done.