Discontinued Using Retainer

You should try to wear the retainer ... you might just be lucky enough that the teeth have not moved very much and perhaps the retainer can correct them.  In this case wear it 24 hours per day for several months then just at night forever.  However, since you've noticed the teeth moving chances are they've moved too far for the retainer to correct.  In this case take the retainer back to your orthodontist and ask about your options: either a new retainer or some means of correcting the tooth movement you've noticed.

SHORT answer: Retainers are needed and should be worn for a lifetime. The first thing I would do it put in that retainer. If it fits with out killing you wear it 24/7. If it kills, don't throw it away. Make an appt with your Ortho.

LONG answer: Even those born with perfect teeth, who have not gone through treatment should have retainers.

You know the saying, " there is one thing you can count on in life and that is change." That is true of teeth too. If you really think about it, why would our teeth stay where they are today. We use them daily. We have the pressure of various textures of food, we swallow and talk all day, which exerting pressure on our teeth. Our tongue and lips are very strong active muscles that are very capable of moving a tooth even over night.

If you had orthodontic treatment, there are elastic fibers that surround every tooth that have some memory and until your teeth are held long enough in their new position they will tend to want to move back, so retainers become very critical in maintaining all the hard work, time and money that have gone in to your smile.

I tell my patients, think of your retainer as your insurance policy that ensures you will keep your teeth s good as they look and feel the day your retainers were made.

PS: I am doing the same thing to my own teeth right now. ;0)