Fixed retainers, also known as bonded retainers, are orthodontic appliances that are attached to the teeth using a dental adhesive. They are typically used to maintain the position of the teeth after orthodontic treatment. Unlike removable retainers, fixed retainers cannot be taken out by the patient and are designed to remain in place for a long period of time. Fixed retainers consist of a thin wire that is bonded to the back of the teeth using a dental cement. They are usually placed on the lower front teeth, where teeth tend to shift the most over time. Fixed retainers are a popular choice among orthodontists because they are effective and require little maintenance.