I'm glad you asked! When orthodontic treatment with braces or invisalign is completed and there is no more active tooth movement, the goal then focuses on holding the teeth in that new, corrected position without them moving back from whence they came. The reason they move is because the collagen fibers that connect teeth to gum tissue and bone needs time to turnover or refresh. The bone also requires at least 12mos to mature. Therefore we emphasize fulltime 24-7 retainer wear (removed for meals) for the first 3 mos when those collagen fibers are really stretched to the max. After 3 mos they can be worn at night only. For how long you ask? I hate the phrase: "for the rest of my life". That's a little daunting, so I just say indefinitely or at least as long as you want to insure straight teeth. The problem is this: we don't know when or what will cause your teeth to shift in the future. It could be a variety of things attributed to the aging process with the end result being a change of forces on your teeth causing them to shift, drift or tip. Sometimes it's a slow process, other times it seems to happen overnight. My practice consists of 30% adult patients who all noticed their teeth looking or feeling worse than they did in years past. So whether it's a colorful acrylic retainer, bonded wire or clear "invisible" retainer, wear it regularly and you will sleep better knowing you're treating your teeth with the attention and respect they deserve. Your smile will show it!