Horseshoe Expander is one of Slow Maxillary Expansion(SME) which aims to accommodate the contra- lateral expansion and midpalatal suture expansion of the palate. The appliance consists of skeleton type screw embedded in split Horseshoe appliance. It is the objectives of the presentation to manifest the changes in dental & craniofacial components subsequent tc the application of Horseshoe Expander. The subjects for this study consisted of 32 patients (mean age :12.7). Frontal, lateral cephalometric headfilm were taken and study casts were fabricated before and after expansion. 24 items were measured, compared preexpansion with postexpansion. Especially, palatal volume was measured by means of "Hydro-measurement metho d" . Tooth axis measurement on the dental casts were made with Universal bevel protractor, and Horseshoe Expander group were compared with R.ME group. This study of changes to maxillary expansion with Horseshoe Expander revealed the following significant results.
1. Triangular-shaped expansion pattern appeared in frontal cephalometric headfilm.
2. Palatal plane, occlusal plane, mandibular plane and upper incisor to FH increased in lateral cephalometric headfilm.
3. Palatal volume increased significantly. A slight bite opening, reduction of occlusal contact points showed in dental casts. 4. A 2.2 : 1 ratio of the amount of intermolar width in maxilla(orthodontic movement) to maxillary width (orthopedic movement)
was determined.
5. Horseshoe Expander group has less buccal tipping tendency than 1IME group, by taking high correlation coefficients in the upper second premolar and first molar.
It was suggested that Horseshoe Expander showed less orthodontic changes, less buccal tipping tendency. In addition, it was effective in maxillary expansion.
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