In comparison to standard Clark Twin Block appliance, the Mahony Twin Block has several innovative features believed to enhance skeletal corrections. First, the lower 70-degree incline block is moved forward -- just distal of the cuspids rather than distal to the second premolars. This creates less need for a support phase appliance, because the premolars are allowed to erupt during the initial treatment phase. To help the patient masticate, the lower incisors are "capped" with clear acrylic. Capping the incisors in this manner prevents lower incisor flaring -- and helps to reduce overbite by exerting intrusion forces on the upper and lower incisors. Anchorage and stability of the lower block are also improved by extending the lingual flanges distal of the terminal molar. “C” clasps are often placed around the distal of the terminal molar to further enhance retention. The anchorage unit of the upper block is improved by the addition of a labial bow -- which results in adding the incisors and cuspids into the anchor system. Because he considers Delta Clasps less prone to failure, Dr. Mahony prefers using them for the retention function.