Distribution of forces on supporting teeth in the midpalatal expander during “Hyrax” screw pre-load

Purpose: The aim of the study was to determine forces which are transferred to supporting teeth during the treatment with the midpalatal device with Hyrax screw and to evaluate orthodontic and orthopaedic effects based on displacement analysis. Design/methodology/approach: The finite element method (FEM) was used to simulation the midpalatal expansion forces activated by the screw pre-loaded during a turn of 180° which corresponds to daily recommended value. Distribution of expansion forces of Hyrax device was calculated as reaction forces on elastic supports with stiffness corresponding to the teeth working on periodontal ligament in alveolar bone. Findings: On the basis of the displacement analysis was observed the movement of supporting teeth by a value higher than 0.1 mm which corresponds to the recommended daily value. The midpalatal suture splitting forces were determined on the first premolars with a value of 32.8 N and on the first premolars of 44.2 N. Research limitations/implications: The studies did not take into account the shape of palate other craniofacial bones and their stiffness. Practical implications: Adjusting the stiffness of the device to degree of ossification midpalatal suture and teeth mobility. Searching for new solutions which eliminate the negative phenomenon of tilting teeth during the expansion of maxilla and recommending a surgically assisted techniques. Originality/value: The simulation confirmed that treatment with Hyrax screw gives a uniform expansion with values of forces corresponded to stiffness of premolar and molar teeth. The studies have indicated a possibility of tendency to tilting the supporting teeth what is a negative phenomenon.