Biomechanical effects of maxillary expansion in cross-bite patients during orthodontic treatment with Hyrax screw

Abstract

The aim of this study was finite element analysis of stress-strain state of the human maxillary complex with and without cleft palate. Loading the skull is carried out by activating orthodontic device HYRAX. Model of the skull and supporting teeth of upper jaw obtained on the basis of tomographic data for dry intact skull of an adult. Design of orthodontic device differ position of screws and rods relative to the palate. Equivalent stresses in the bones of the craniofacial complex are assessed. It is shown that large stresses occur in the maxillary complex, if the screw and rods of orthodontic devices are located in a horizontal plane for skull with and without cleft. Also in the intact skull big stresses appear in the bone of the upper jaw with location of the screw and rods of orthodontic device in a horizontal plane. In the rest of the skull bones stresses are insignificant. By moving the device screw to the palate the values of maximum stresses are reduced, but the region of big stresses displaced to the pterygoid plate and pharyngeal tubercle. In the skull with cleft for different positions of screws and rods orthodontic device the upper jaw is loaded fragmentary. High stresses are observed in the region of the maxilla near the zygomatic arches and along the edges of eye-sockets. When placing screw of orthodontic device close to palate the stresses decreases, but are observed in most part of the zygomatic arches.