When you first get your retainer fitted you need to wear your retainer at least 12 hours out of every day for the first eight weeks following the completion of your treatment.
However, you can remove them when you eat or brush your teeth.
After that initial three months, you will wear your retainer for 12 hours a day (or night) for the next nine months.
By the end of this first year, your teeth should be more securely placed and less likely to quickly relapse
Your teeth can shift back if you stop wearing your retainer.
It's important to keep wearing your retainer for as long as your dentist says you should.
Though the process becomes slower and slower, if you stop wearing your retainer, your teeth will gradually move back to their original position. In a way, teeth remember their original position.
If you don't wear your retainer, your teeth will eventually shift back to their old positions.
This is particularly true in the months and even years directly following treatment with aligners or braces.
If you stop wearing your retainer before your teeth have had time to set into place then your teeth can shift back out of place defeating the purpose of the retainer in the first place.
If your teeth shift back out of place after you stop wearing your retainer then your teeth will require new orthodontic treatment to fix your bite.
Then you'll have to start all over again and wear the retainer longer.
For at least the first 4 to 6 months of getting the retainer you need to wear the retainer for 22 hours per day.
Then after the 4 to 6 months of wearing the retainer for 22 hours per day you can switch to just wearing the retainer for 8 to 10 hours per day or just overnight.
Most people just wear the retainer overnight which is usually enough to keep their teeth aligned after the first 4 to 6 months.