Česká Stomatologie a Praktické Zubní Lékařství (Sep 2022)
MEASUREMENT OF DIMENSIONAL STABILITY OF DENTAL ARCH MODELS PRINTED FROM THERMOPLASTIC MATERIALS WITH THE FUSED DEPOSITION MODELING METHOD DURING THE VACUUMING PROCESS
Abstract
Introduction and aim: In recent decades, the whole field of medicine has been undergoing a digital revolution. This phenomenon is making its way into dental fields as well, including orthodontics, and gradually more and more workflow procedures are being digitalized. The digital models of dental arches can be obtained with the help of an intraoral scanner, and afterwards, using a 3D printer, they can be transformed into physical models. In the field of orthodontics, dental models are needed as study models for diagnostic analysis and determining the therapeutical plan. Dental models at the end of orthodontic therapy are very important as working models for the production of retention devices. The thermoplastic retention plates are very frequently given to patients as retention apparatus and are very popular among them. They are being manufactured at high temperatures in a vacuum machine in a process also known as vacuuming. Conventionally this manufacturing tends to be performed on classic gypsum models. With the growing popularity of digital dental models and their subsequent 3D printing, it is important to know whether dental models made in this way are also suitable for the production of thermoplastic retention plates. Currently, the most widely used method for 3D printing is called Fused Deposition Modeling, using molten plastics as a material for the printing.The aim of this research was to evaluate 3 thermoplastic materials - ABS, ASA, and Z-Ultrat and to measure their dimensional stability while being exposed to the conditions of vacuuming during the production of the thermoplastic plates. It was important to determine whichof them would retain its dimensional stability under given conditions in the best way.Methods: To obtain the necessary data, we first made intraoral scans of the upper dental arch of two patients using an iTero intraoral scanner. With the use of Zortrax M200 3D printer, these scans were then used to produce physical 3D models. The following parameters were setfor the 3D printing: layer thickness - 0.09 mm, density of the infill - 70%, and orientation of the model in the Z axis - 45°. The physical 3D models were then digitized again with GOM ATOS TripleScan extraoral 3D scanner, placed in a vacuum machine, and then scanned again. GOM Inspectsoftware was used to evaluate the dimensional accuracy of manufactured parts. The maximum clinically acceptable deviation between the first 3D scan and the scan of the physical model after vacuuming was determined by the authors to be +/- 0.50 mm.Results: Dental models from all 3 examined thermoplastic materials have shown a statistically significant change in their dimensions. However, the magnitude of these deviations is acceptable for clinical practice. All models printed from ABS and Z-Ultrat met the maximum clinically permissible deviation of +/- 0.50 mm.Conclusions: Certified material Z-Ultrat, having a chemical composition of PC-ABS, showed the best dimensional stability. Based on the obtained data, it can be concluded that the models of dental arches printed by the FDM method can be used in practice as working models for the production of thermoplastic retention plates.
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