Evaluation of variables of different rapid upper jaw expansion appli̇ances manufactured in a digital environment

In this study, it is aimed to produce the hyrax appliance designed with using different metal alloy in digital environment by computer aided design (CAD) and computer aided manufacturing (CAM) method by revealing the workflow step by step and to measure the stress and displacements that may occur in the maxilla and teeth after activation by finite element analysis. This study which is aim to pioneer the application of -the latest technologies in the world, the step-by-step procedure of producing a directly printed metal appliance without the need for physical castings is presented, revealing the workflow that should be done after full digitalization in orthodontic practice. A stereolithographic model was created by scanning the phantom jaw model with three-dimensional scanners and recorded in the digital system. The Hyrax appliance, which was designed digitally on the created virtual model, was produced digitally using stainless steel, chromium-cobalt and titanium, and real screw activation was simulated on the appliance. Representing the first screw activation in clinical practice, 0,5 mm widening was obtained by turning the first 2 turns, and 5 mm widening was created as a result of 20 turns. The stresses and displacements in the appliances and the displacements in the models were calculated with finite element analysis, which is a mathematical stress analysis method. When 0,5 mm and 5 mm transversal widths were created in the appliances, the von Mises stresses were highest in the chromium-cobalt-containing appliance (1547,9 MPa), and the least in the titanium-containing appliance (209,6 MPa). In these transversal widths, the displacements due to the deformation of the appliance occurred the most in the chromium-cobalt-containing appliance (4,0827 mm), and the least in the stainless steel-containing appliance (0,27768 mm). When looking at the displacements in the virtual model, there is a decrease from anterior to posterior, with the highest displacement in the anterior region and the chromium-cobalt appliance (0,86795 mm), the least displacement in the posterior region in the stainless steel appliance (0,13231 mm). As a result, in our study, von Mises stress occurred at least in the titanium-containing appliance during transverse expansion in the treatment of RME. If the problems related to cost and production can be overcome, appliances made of titanium can be used in expansion treatments. Digital appliance production offers great potential for the production of more effective appliances, with the improvement of the biocompatibility and durability of the selected material, as well as the diversity of designs. With this experiment, it has been shown for the first time that the titanium-containing material used in the digitally produced hyrax appliance can be successfully produced. Keywords: Transverse Maxillary Deficiency, Rapid Maxillary Expansion, Hyrax Appliance, Digital Orthodontics, Finite Elements Analysis.