Twin Blocks


Clark Design


The Twin Block appliances utilize acrylic inter-occlusally to aid in mandibular advancement. The appliance fits the patients much like a Hawley retainer with occlusal coverage. The key to the Twin Block therapy is the addition of a 70° angles cut into the inter-occlusal acrylic at the second bicuspid area. This is the key to the patient functioning in a class I position. The acrylic can be adjusted to control the vertical position of the posterior teeth. This allows the clinician to determine if the design is to open, close or maintain the posterior teeth position. Adams clasp and ball clasp are added for retention as well as a labial bow. Expansion screws can be added if arch development is also desired.



McNamara Design


Dr. James McNamara from the University of Michigan modified the Twin Block by adding Acrylic to the lower labial bow for additional retention. The appliance also utilizes ball clasp on the lower arch for retention. Expansion screws can be added as well if arch development is desired. As with the standard Twin Block the vertical dimension of the posterior teeth can also be controlled.