The rapid palatal expansion appliance (RPE) with an interchangeable Hyrax® screw
Elements:
0.8 mm / 0.032” rectangular stainless steel wire, Hyrax® screw
Function:
Correction of extreme cross-bites
Description:
When the expansion capacity of a single screw is not sufficient, the treatment can be performed in several steps with this appliance
The bands once adapted into the impression are waxed out slightly and poured as usual. The bands should be blocked out with a very thin layer of wax, so that although they are fixed well on the cast, they can be removed easily from the cast after finishing. Before, the bands should be replenished with brackets on the palatal side.
The rectangular wire should be adapted on both sides from the first premolar to the first molar into these brackets. Special attention should be paid that this rectangular wire is ligated passively into these brackets.
Now the Hyrax® screw is adapted in a distance of 1 mm to the palate and fixed with the Spot Welding Unit to the rectangular wire. This way the appliance can be soldered or welded and then inserted.
After a couple of weeks, when the end of the screw spindle is reached, the appliance is removed and an impression is taken, then it is inserted again. In this impression, transmission brackets are set in, slightly waxed out, and then poured.
Now on this prepared cast, a second appliance can be made. In the meantime the first appliance is used passively to maintain the arch width. Before making the second appliance, the screw has to be opened 3 or 4 turns and then be adapted to the palate.
After this, a direct replacement can take place in the patient’s mouth. While inserting the appliance, the screw is unscrewed to get past the brackets and then is opened up again immediately. If the dimension of the planned expansion makes it necessary, a third appliance can be inserted.
