Modified Cast-Metal Haas-Type Expander for Correction of Impacted Upper First Molars in the Mixed Dentition

The advantages of a rapid maxillary expander (RME) anchored to the deciduous teeth in the mixed dentition have been described in the literature, as has the use of a cast-metal Haas-type RME bonded to six deciduous teeth.[ref]1-4[/ref] If the upper first permanent molar remains impacted against the second deciduous molar, however, the distal root of the deciduous molar may experience early resorption, leaving the permanent molar unable to erupt spontaneously. It then becomes impossible to band the deciduous second molar, especially considering the poorly retentive coronal anatomy of the deciduous teeth. The use of bands could not only increase the risk of appliance failure, but create another obstacle to first-molar eruption. An alternative approach would be to extract the deciduous second molars and expand the permanent teeth, but this could lead to early loss of the leeway space, with the consequent need to regain space by distalizing the upper molars or by using extraoral traction in a second treatment phase, or to wait for full eruption of the first molars. It might also require a transpalatal bar to be used before expansion to correct a buccal molar inclination or molar rotation.