COMPARISON OF HYRAX AND BONDED EXPANSION APPLIANCES

The majority of rapid maxillary expansion studies have reported the us e of appliances with metal bands attached to the posterior teeth. Toot h extrusion, dental tipping, and an increase in the vertical dimension are often encountered, which may not coincide with treatment objectiv es. Bonded appliances using interocclusal acrylic may control the vert ical dimension and expand the maxillary halves in a more bodily and sy mmetrical fashion. The purpose of this clinical trial was to determine , by radiographic analysis, the differences between a conventional ban ded expander (Hyrax) and a bonded acrylic expander. Fourteen patients who exhibited a need for expansion were enrolled in the study. The res ults suggest that the increase in the vertical dimension often seen wi th the more conventional Hyrax appliance may be minimized or negated w ith the bonded appliance. However, there appeared to be no significant difference between the amount of dental tipping or symmetrical expans ion between the two appliances, as previously theorized.