الفهرس 
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Abstract
The aim of this study was to evaluate the effects produced by three slow maxillary expanders, (Nitanium palatal expander 2, Compound palatal bar, and Quad helix) on the skeletal and dentoalveolar structures in an attempt to high-lighten their ideal clinical implication.
The study consisted of thirty healthy Egyptian girls each exhibiting unilateral or bilateral posterior crossbite, and required palatal expansion as part of their comprehensive orthodontic treatment. The girls were equally divided into one of three groups; group A (NPE 2) whose mean age was 13.3 years, group B (CPB) whose mean age was 14.2 years, and group C (QH) whose mean age was 13.7 years.
Each girl was clinically examined, and an orthodontic diagnostic study cast was recorded. Both extraoral and intraoral photography were taken. In addition to occlusal radiographs, lateral and posteroanterior cephalometric radiographs were obtained at pre-treatment (T1), postexpansion (T2), and postretention (T3).
The different expanders were selected, placed, and activated according to manufacturer’s instructions. Force determination per unite activation in millimetres of one expander from each type was achieved via a compression and tension gauge. A 3D computer program was specially designed for more accurate evaluation of the dental effects induced by three types of maxillary expanders.
Results revealed the following; Radiographic evidence of midpalatal suture separation was less frequent in the CPB than in the NPE2 and QH groups. Slow maxillary expansion didn’t affect the sagittal and vertical position of the maxilla. The mandible moved downward and backward, and the anterior facial height increased appreciably in NPE2 and QH groups. The CPB expander didn’t rotate the mandible downwards and backwards. Spontaneous increase in the lower intermolar width followed slow maxillary expansion in the three groups. NPE2 showed the significantly lowest treatment duration followed by CPB. The QH expanders tipped the molars buccally to a considerably greater extent than NPE2 and CPB expanders. QH expanders rotated and extruded the molars to a larger extent whereas, CPB showed the lowest extrusion and rotation. The reliability of generating 3D dental images using photographic imaging of the dental casts for 3D tooth movement analysis.