Frankel Appliance: Understanding the Four Types and Their Clinical Indications

The Frankel Function Regulator (1967) is unique among functional appliances in being tissue-borne. FR-I: Standard for Class II/1 with crowding. Buccal shields, lower lip pads, palatal bow (1.2mm), labial bow (1.0mm). FR-II: FR-I plus anterior bite guide and lingual wire for Class II/1 with large overjet and deep overbite. FR-III: Reversed configuration: upper lip pads stimulate maxillary protraction; lower buccal shields restrain mandibular growth. For Class III. Critical: using FR-I/II for Class III worsens the condition. FR-IV: Extended buccal shields and anterior bite blocks for open bite. Deep impressions capturing full vestibular depth are critical for all types. Optimal treatment window: 7-12 years.