I was wondering if you have to wear a retainer on the top teeth as well as on the bottom teeth to retain your new bite, or just one or the other. Thanks.

both for at least a year. The first month all day then just at night.

I wear top and bottom at night... I think I will continue to for life. It has been over 10 years, and if I don't wear them for awhile, they tend to move back a little.

They have new retainers now that are just plastic and are moulded to your teeth. They are not uncomfortable at all. It is very wise to wear retainers after braces, otherwise you will likely have to do the whole orthodontics procedure again and that's not good.