Simulation model and other material preparation
The impressions of both jaws were taken from the patient by an experienced specialist using silicone impression material (Silagum-Light and Silagum-MixStar Putty Soft; DMG Medical Devices, Rome, Italy). The gypsum casts (Modern Materials, Die-Stone; Kulzer GmbH, Hanau, Germany) of both jaws were then poured from the impressions, and served as master models. To capture the precise details of the master models, optical scanning was performed via a highly accurate dental laboratory scanner (3Shape E4; 3Shape, Copenhagen, Denmark). As the working master model, the mandibular model was scanned three times to confirm its reproducibility. The 3D data of the model scanning was exported into STL format. A total of 140 mandibular and 35 maxillary acrylic resin models (mandibular models with topical artificial gingiva) were fabricated by 3D printers (AccuFab-C1s; SHINING 3D, Hangzhou, China) from a dental laboratory based on the STL files of the model scanning, as shown in Fig. 3D printed acrylic resin models (with topical artificial gingiva) of both jaws