This fact is from Retention & Relapse in Orthodontics. It is a commonly tested concept in NEET MDS examinations. Understanding this fact is crucial for answering MCQs correctly.
Most common relapse = lower anterior crowding
Bonded retainer = permanent fixed retainer
Hawley retainer = removable with labial bow
Vacuum formed retainer = Essix = clear overlay
Relapse causes: late mandibular growth, soft tissue pressure, periodontal fiber recoil.