After your braces or Invisalign treatment ends, your retainer becomes your greatest ally and the key to protecting your smile. But like anything you use regularly, retainers don’t last forever. In fact, depending on the type you have and how well you care for it, your retainer may eventually need to be replaced. Knowing what to expect can help you stay ahead of the curve and keep your teeth right where they should be. Here’s what you need to know.