Impact of the Internal Structure Density in the Process of Fabrication of Orthodontic Master Models by Fused Deposition Modeling

The article focuses on the influence of infill (internal structure of components) in the dimensional accuracy of dental master models during the processes of their fabrication by Fused Deposition Modeling (FDM) technology, and their vacuuming process for production of clear orthodontic aligners. The components, in this case, were the upper jaws (maxillary teeth) of two individual patients (Tzina, Dimitris), which were obtained by intraoral 3D scanning. Patient Tzina at the time of intra-oral scanning was 27 years old and Dimitris was 23 years old. The method of 3D printing was the FDM, and the material used in this research was thermoplastic high impact polystyrene (HIPS). Three different percentages of infill density were set, 60%, 80%, and 100%. For each setting, there were five specimens (thirty 3D printed dental models in total, 15 for Tzina and 15 for Dimitris). After the 3D printing, the models were digitized and measured by GOM ATOS II Triple Scan MV 170 optical 3D scanner and compared with the values of the initial digital models. Then the dental master models underwent the process of Essix-aligners formation (single press) and were rescanned and measured again. The outcome of this research was to examine if the dental master models remain dimensionally accurate after these processes, and which infill provides the optimal and medically approved accuracy.