There are a few varieties of retainers, each with their own strengths and considerations.
This retainer consist of a wire which sits behind your front teeth. It may be placed on both upper and lower teeth and is not removable.
These retainers are clear removable retainers which cover all the surfaces of your teeth.
This retainer is removable and is made of a plate which covers the roof of your mouth as well as a wire which sits across your front teeth to control their movement. These retainers are designed for the upper teeth.