Appliance Purpose / Function:
The Twin Block Appliance differs from other functional appliances in that it is actually two separate appliances (maxillary and mandibular) working together to maintain an advanced mandibular position. This is achieved by incorporating acrylic blocks into the occlusal surface of the appliances which interface with each other in the bicuspid region at a 70 degree angle. This interface prevents the mandible from sliding back into its accustomed position. The reduced bulk of the appliance allows patients to wear the Twin Block full-time including while eating thereby harnessing the forces of mastication and occlusion for faster treatment results. As treatment progresses, the orthodontist can selectively reduce the bite surfaces to allow for the desirable eruption of posterior teeth.
- .028 Ball Clasps between the lateral incisors and canines
- Adams Clasps on the lower first bicuspids and the upper first molars
- Labial bow on the upper arch from cuspid to cuspid
- Screw- 7mm acrylic borne expansion screw.
- Wire: Stainless steel wire
- Dental Acrylic
Appliance Fabrication Standards:
- Note: The upper portion of the appliance is poured and trimmed first and petroleum jelly is applied to the 70 degree ramp so that when the lower portion is poured, an opposing 70 ramp can be formed by closing the upper model on the fixator with the appliance in place against the built up acrylic on the lower model.
- The acrylic plate must cover the palate and be a uniform thickness of approximately 2mm except on the occlusal surface where it must be built up to the opening indicated by the Client’s construction bite, and at the expansion screw (if indicated by design) where it must be thick enough to cover the acrylic borne screw
- In the anterior region, the lingual acrylic must be trimmed to where it covers the cingulum of the anterior teeth, and the acrylic is scalloped around the first bicuspid or premolar
- The occlusal coverage must begin at the mesial side of the second bicuspid or premolar in a 70 degree ramp that slopes towards the posterior. The remaining portion must be as smooth and flat as possible while still allowing for contact with the opposing arch. This occlusal block must be the approximate width of the teeth that it covers and allow for the maximum possible surface area in the interface area of the ramp. A narrow ramp will not be capable of holding the mandible in the necessary protruded position
- Posterior border tapered towards the tissue with a rounded edge (thin, sharp knife-like edges not acceptable)
- Inferior border tapered towards the tissue with a rounded edge (thin, sharp knife -like edges not acceptable)
- The lingual flange covers 2/3 to 3/4 of the sagittal wall and ends at the distal side of the second bicuspid or premolar
- Acrylic must be kept away form the lingual frenum for patient comfort
- Overall uniform thickness of approximately 2mm except in the area of the occlusal coverage where it must be built up to the opening indicated by the Client’s construction bite
- The occlusal coverage must begin at the mesial side of the first bicuspid or premolar. The surface must be as smooth and flat as possible while still allowing for contact with the maxillary first bicuspids or premolars. The posterior portion ends in a 70 degree ramp that opposes and interfaces with the one on the maxillary appliance. As with the maxillary appliance, the occlusal block must be the approximate width of the teeth that it covers and allow for the maximum possible surface area in the interface area of the ramp.
- The standard design has Adams clasps on the first molars and a labial arch from cuspid to cuspid. Clasping schemes may vary based on Client preference and the teeth present on the case
- A 7mm acrylic borne screw must be placed on the midline in the depth of the palate as close to the tissue as possible without touching. The split of the screw must be in line with the patient’s midpalatal suture
- The standard design has Adams clasps on the first bicuspids and ball clasps between the lateral incisors and canines. Clasping schemes may vary based on Client preference and the teeth present on the case