The day braces are removed is always a joyful one in our office, for patients and team alike. This is also when the next phase, called retention, is just beginning. Retention is a critical follow-through stage that typically involves wearing a custom-made orthodontic appliance called a retainer. The retainer keeps the teeth from moving back to where they started. Teeth aren't set rigidly in the jawbone — instead, they're held in place by a network of fibers called the periodontal ligaments.