Lehman Appliance
A specific type of headgear-activator has been developped by the aid of which it is possible to perform differential initial dento-orthopaedic treatment of CL: 2:1 case according to the individual skeletal pattern presented by the patient.
L.A. 1:
The appliance mainly has three component parts; a maxillary plate, a mandibular pelotte, and two outerbows. The acrylic plate covers the palate, the maxillary occlusal and incisal surfaces and 1/3 of the buccal and labial parts of the maxillary clinical crowns. The mandibular pelotte concists of an acrylic section with supporting arch and is connected to the maxillary plate by two s-formed springs. The maxillary plate is fitted with two imbedded outerbows unto wich an occipital traction can be applied. The direction and force of the extra-oral traction should be designed according to the individual needs. A low-inclined long outerbow may enhance a clockwise rotation of the maxillary complex while a high-inclined short outerbow is most effective in upper incisor intrusion. In cases with a deficient mandible the extra-oral traction is used for anchorage purposes only while the stepwise activation of the S-formed springs of the mandibular pelotte will stimulate the mandible to take a more anterior position. An expanding influence on the maxillary arch in cases of transversal discrepancies is obtained by a jackscrew in the split palate of the acrylic plate. A labial wire, torquesprings or other fingersprings can be added for tooth movements in the upper arch.
This type of headgear-activator can be used as a conventional fixed appliance as well as in combination with lingual arch therapy, two modifications have been developped.
L.A. 2:
The headgear-activator for conventional fixed appliance therapy consists of a maxillary plate, a screw, the pelotte with supporting arch, two S-formed springs, two knob-clasps and two modified retaining springs, two knob-clasps and two modified retaining springs. The long retaining springs are lying above the buccal tube on the molarbands and are extending mesially for ease in removal. The acrylic plate does not cover the occlusal and incisal surfaces.
L.A. 3:
The headgear-activator for lingual arch therapy is basically in the same as the L.A. 2. There is no contact of the maxillary plate with the lingual arch brackets.
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