CATEGORY AUSTRALASIAN DENTIST 49 LINICAL The medical indications include: u Allergic rhinitis u Septal deformity u Recurrent ear, nasal or sinus infections u Poor nasal airway u As a preliminarymeasure to septoplasty u Cleft palate patients with collapsed maxillary arch. 2. Contraindications of RME Appliances u Patients with poor compliance u Steep mandibular plane angle and convex profile. u Cases of single tooth crossbite and anterior open bite u Subjects with skeletal asymmetry of maxilla and mandible u Patients with severe anteroposterior and vertical skeletal discrepancies. 3. Principle of RME causes the retention of the appliance to get compromised. Patient compliance is paramount to all removable appliances. Efficiency is less compared to fixed. 2. Fixed RME Appliances Fixed rapid maxillary expansion appliances are fixed expanders which cannot be removed by the patient. The fixed RME appliances can be either tooth-borne or tooth and tissue-borne. u Tooth-borne appliances: Isaacson type or the Hyrax type of appliance. u Tooth and tissue-borne appliances: Derichsweiler or the Hass type of appliances stainless steel wire (0.045 inch/1.15 mm) is welded and soldered along the palatal aspects of the band. The free ends are turned back to be embedded in acrylic plate which contains an expansion screw in the midline. Both Derichsweiller and Haas types use similar kinds of screws. 4. Classification 1. Removable RME – Removable appliances are not effective for RME because they are not rigid enough to produce skeletal expansion. 2. Fixed RME Types: Bonded or Banded type Tooth-borne or Tooth and TissueBorne Type 1. Removable RME Appliances The appliance basically consists of a screw in the midline with retentive claps on the posterior teeth. The acrylic plate is split in the middle and activations of the screw forces the two halves to move apart, resulting in the desired expansion. This appliance is more effective when used in the early mixed dentition phase. Its efficiency in the late mixed dentition and older patients is suspect because of the ossification of the mid-palatal suture and the resulting delay in splitting Tooth and tissue borne Haas appliance Tooth borne Banded RME appliance Fabrication First premolars (deciduous molars) and first permanent molars are banded. They are joined labially and palatally by soldering with heavier gauge wire. The basic RME appliance is the screw which is placed in the midline. The difference in appliance design is based on the various types of screws and mode of attachment. The different types of banded RMEs are as follows: 1. Derichsweiler type: This expansion appliance consists of molar bands on right and left permanent first molars and first premolars with wire tags soldered into the palatal surface. The jack expansion screw is connected to the bands by means of tags that are welded and soldered to the palatal aspect of the band on one side and embedded in acrylic on the palatal aspects of all non-banded teeth except the incisors. Acrylic adapts to the palate and is in two halves to permit activation of the screw in the midline. Derichsweiler appliance Isaacson appliance Hyrax expander 2. Haas type: This appliance is a rigid appliance which not only transmits forces on to the teeth but also on to the palatal shelves directly. Heavy 3. Isaacson type: This type uses the Minne-Expander, which is a special spring-loaded screw. It is adapted and soldered directly to the molar and premolar bands with a closing nut which tends to compress the spring, and activates the expander. Acrylic plates are not used in this. The drawback of the basic expansion screw is the build-up of pressure, which is hazardous to tissue. To overcome this, and to make the force application smooth and constant, Issacson type was introduced. 4. Biedermann type: It was introduced by Willian Biedermann in 1968. This tooth-borne appliance uses a HYRAX (hygienic rapid expansion) screw, named after the ability to keep it clean. The screw has heavy wire extensions, which can be adapted to follow the contour of the palate and are soldered to either metal bands or cast cap splints or a wire framework that has acrylic splints or is embedded in acrylic splints. The expansion screw is turned with a key either once or twice daily (0.2 mm expansion/turn) for the entire expansion
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