الفهرس 
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Abstract
Rapid maxillary expansion (RME) is one of the most frequently used methods in
correction of deficient maxillary arch width manifested in the form of unilateral or bilateral posterior crossbite. The main scope of most expanders developed and modified to date, is to produce more skeletal (orthopedic) correction than dental (orthodontic) expansion. Orthopedic changes are easily produced and better carried out on children than on older age groups due to incomplete interdigitation of the palatal sutures. Conventional expansion appliances of the tooth-borne category depend on dental units for anchorage. This, however, adversely affect the supporting peridontium and bone of these teeth. With the aid of the temporary skeletal anchorage devices such as (mini-screws), which are fixed to the anterior palatal bones, the huge separating forces generated during rapid maxillary expansion are
transferred to the anterior palatal shelves through the anchorage devices, thus, producing less dental drawbacks. This is thought to be of particular interest when the maxillary width
reaches its adult size and the palatal suture is interdigitated as in the case of adolescent patients needing skeletal expansion of the maxillary arch. Our main objective was to evaluate
the dento-skeletal effect of maxillary expansion using bone anchored Hybrid Hyrax expander. A significant increase of all skeletal and dental transverse variables from T1 to T2 was found for the linear measurements on the study cast and on that of the PA cephalometric
measurements. Correction of the crossbite was successfully achieved in all subjects. The Hybrid Hyrax expander is effective in providing both skeletal and dental correction of maxillary crossbite in females of the critical age of adolescence.