Invisalign is designed to move and straighten the teeth in small stages. With Invisalign you typically will have sets of clear aligners that you wear for two weeks at a time then go on to the next set of aligners. This process slowly puts pressure on the teeth moving them to there new position. The amount of aligners depends on how much movement is needed to straighten the teeth. Invisalign uses 1mm clear essix material to create these aligners. After the teeth are straighten, a set of retainers are required to prevent the teeth from going back to their original location.
Clear Essix retainers and designed just to prevent the teeth from shifting. Retainers will not move or straighten you teeth, they will prevent them from shifting further. Retainers are made using 1mm clear essix material the same as Invisalign.
Both Essix retainers and invisalign are made from the same material and are cleaned and taken care for the same. Retainers can last for many years while the invislign aligners are designed to only be used for a short period of time.