TYPES OF RME APPLIANCES:
Derichsweiler type:• The first premolars and the first molars are banded.• Wire tags are soldered onto the palatal aspect of the bands.
• These wire tags get inserted into a split palatal acrylic plate incorporating a screw at its centre.
Hass type• The first premolar and molar of either side are banded.• A thick stainless steel wire of 1.2 mm diameter is soldered on the buccal and lingual aspects connecting the premolar and molar bands.• The lingual wire is kept longer so as to extend past the bands both anteriorly and posteriorly. These extensions are bent palatally to get embedded in the palatal acrylic.• The split palatal acrylic has a midline screw.
• The plural does not extend over the rugae area.
Isaacson type:
• This is a tooth borne appliance without any acryl palatal covering.• This design makes use of a spring loaded screw called a MINNE expander (developed at the University of Minnesota, Dental School).• The first premolars and molars are banded.• Metal flanges are soldered onto the bands on the buccal and lingual sides.• The expander consists of a coil spring having a nut that can compress the spring.• This coil spring is made to extend between the lingual metal flanges that have been soldered.
• The expander eactivated by closing the nut so that the spring gets compressed.
Hyrax type:
• This type of appliance makes use of a special type of screw called HYRAX (Hygienic Rapid Expander).
• The screws have heavy gauge wire extensions that are adapted to follow the palatal contour and are soldered to bands on premolars and molars.
REFERENCES:
- Orthodontics: The Art & Science, SI Bhalajhi (7th Edition)
- ResearchGate
- Slideshare
- accutechortho.com