A retainer is often advised for people who have had orthodontic treatment, such as braces or clear aligners, to straighten their teeth. After the orthodontic treatment and the braces or aligners are removed, the teeth return to their original positions.  Whether a patient needs one depends on various factors, including the initial alignment of the teeth, the complexity of the orthodontic treatment, and the individual’s oral habits. The orthodontist will assess each patient’s specific needs and recommend the appropriate type and duration of its use to maintain the desired outcome of the orthodontic treatment.