Teens who get braces often get a lecture from their parents, orthodontists, or from those who have had braces before them: always wear your retainer. Whether it’s at night or permanently, wearing your retainer is a vital part of the teeth-straightening process — your orthodontist wouldn’t prescribe it if it wasn’t.

The best way to explain it is to explain in simple terms how braces work. When your orthodontist installs your braces, he or she is basically installing a force system designed to push your teeth into a new position along the jawbone so that they’re aligned properly. In order for your teeth to move, they have to lose some of the stabilizing bone that keeps them in their original positions. Not to worry, though: once your teeth arrive at their intended destination, new stabilizing bone will form within 12 months.

Of course, once your teeth have reached their proper positions, you no longer need braces. Your orthodontist will remove them and provide you with a retainer. Because your stabilizing bone will deposit within the year after your braces are off, it’s vital that you wear your retainer during this time. Faithful wear keeps your teeth in the right spot as they’re more or less cemented into place; failing to wear your retainer could allow your teeth to slide out of alignment just before they’re solidified into their intended positions.

Once they’re stabilized by bone deposits, your teeth will be much less likely to move. However, you will typically still have to wear your retainers up to five times per week indefinitely. That’s because, after the initial year of movement potential, our jaws still move inward and forward as we age. This movement happens very slowly, but it’s better not to risk it and to wear your retainers as often as possible.

If you need any more convincing to pop your retainer in as an adult, know this: almost one third of the adults who seek orthodontic treatments in their older years are doing so because they failed to wear their retainers. Therefore, they need a brand new set of braces to fix the mistakes that they made years and years ago. Nobody wants to pay for braces twice, so remain diligent about your weekly retainer wear.

You’ll probably end up replacing ill-fitting, old, or lost retainers multiple times over the course of your lifetime, but the cost of a simple metal device like a retainer pales in comparison to a second set of braces. Wear yours and you won’t have to worry about a shift in your smile for the many years ahead.