Abstract
BackgroundRapid maxillary expansion (RME) has effects on the dental and periodontal structures of the parts involved, which vary according to the design and position of the expansion screw. The purpose of the study was to determine the optimal three-dimensional position of the Hyrax screw to obtain precise control of the dental movement and effect on the bone cortex using the finite element method (FEM).Material and MethodsRME was performed from the patient whom two Cone-Beam computerized tomography scans (CBCT) were obtained: T1 before expansion, and T2 three months after stabilization of RME. The FEM model was designed with T1 and of Hyrax photographs. FEM was obtained by comparing the simulation, T2, and clinical results. Three sagittal screw positions (anterior-middle-posterior) and vertical (upper-medium-low) were evaluated.ResultsA coronal- buccal displacement of premolars and first molars was found which decreased in the occlusal-apical direction, presenting different types of dental movement in the screw positions; besides, a tendency of translational movement in the posterior-high location was observed. In the posterior-high position a higher concentration of efforts and homogeneous deformations in the periodontal ligament and vestibular cortex of the cervical area of first molars, first and second premolars were observed, with variations according to the screw position and the distribution of stresses.ConclusionsThe ideal location of the expansion screw for controlling dental movement and periodontal side effects was the high-posterior position. Key words:Maxillary expansion, dental movement, finite element analysis, orthodontic appliances.
Highlights
Rapid maxillary expansion (RME) is the most commonly used treatment for the correction of the transverse deficiencies of the upper jaw; it is the only one that produces a mechanical separation of the palatine bones
Various studies have determined the best position of the height of the hyrax screw with respect to the centre of resistance of the anchor molars, using the finite element method (FEM) [3,10], where it is reported that the hyrax screw must be positioned at the same level as the center of resistance of the molars, avoiding excessive vestibular movement in both apical and coronal, generating a mass movement
Simulations were performed on three screw positions in the sagittal plane
Summary
Rapid maxillary expansion (RME) is the most commonly used treatment for the correction of the transverse deficiencies of the upper jaw; it is the only one that produces a mechanical separation of the palatine bones. The application of the FEM can predict the tissue responses through the observation of the efforts created from orthodontic mechanisms applied [11] This method allows to simulate with accuracy and reliability the effects of any system used in dental practice, and in the case of RME systems allows to simulate the different positions of the expansion screw in terms of the control of dental movement and effects on the cortical bone [3,10,12]. The purpose of the study was to determine the optimal three-dimensional position of the Hyrax screw to obtain precise control of the dental movement and effect on the bone cortex using the finite element method (FEM). Conclusions: The ideal location of the expansion screw for controlling dental movement and periodontal side effects was the high-posterior position
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