Essix retainers are transparent pieces produces from a mold; they fix over the entire arch of the teeth. They are very similar to Invisalign trays and are favored due to their ease of use. Patients usually remove them when eating and simply put them back when they are done.
These are the most common types of retainers. They utilize a metal wire that surrounds the anterior teeth and holds them in place, anchored by an acrylic (skin colored) arch that sits in the palate of your mouth.
Fixed retainers cannot be removed and are suggested when there is a greater chance of the teeth reverting back to their old positions after treatment.