## 2 Materials and Methods  
Two protocols (in vitro and in vivo) for crown preparation on the mandibular first molar were performed. For the in vitro part of the study, a typodont (AG-3; Frasaco, Tettang, Germany) inserted in the mandibular articulation of a dental mannequin (Phattom head PK-2 TSE; Frasaco) was used. A full crown preparation with a chamfer margin was conducted on the left mandibular first molar of the typodont. The typodont was digitized with the help of a high-accuracy desktop scanner (Freedom HD; DOF) in order to obtain the reference data consisting of a standard tessellation language (STL) file (Figure 1a). For the in vivo part of the study, a clinical case was selected after obtaining informed consent and Ethical Committee approval from CECS UMFT Nr. 03/2023. A full crown vertical preparation on the right mandibular first molar was performed. Figure 1: Three-dimensional meshes of the in vitro and in vivo reference models. (**a**) The typodont. (**b**) The cast model of the clinical case. A conventional two-step impression technique using an elastomeric addition-cured silicone-based precision material (Variotime, Kulzer, Hanau, Germany) with a single retraction cord was performed. A cast model was produced using a high-strength, high-accuracy scannable plaster type IV (Ventura SuperDie Rock; Madespa, Toledo, Spain). The cast model was digitized with the same desktop scanner (Freedom HD; DOF) in order to obtain reference data for the clinical case. The desktop scanner was calibrated according to the manufacturer's instructions; a high level of accuracy, <7 microns, is specified for this scanner. With the use of a Medit I/00 intraoral scanner, three different scanning protocols were conducted on the typodont. The scanning protocols consisted of:  
1. A single continuous scan without interruption, capturing as many data as possible without overlapping the already registered areas. The scanning path started distally on the left mandibular third molar and followed the occlusal plane until reaching the left mandibular central incisor at the median line, returning on the lingual side of the prosthetic plane, and finally capturing the buccal part of the prosthetic plane (Figure 2a). This protocol was named the \"SINGLESCAN\" protocol. All subsequent scans obtained by this protocol were grouped in the \"SINGLESCAN\" measured data group. 2. A second scan filling in the missing data and overlapping the already captured areas. The rescanning path started distally on the left mandibular second molar and followed the occlusal plane until reaching the left mandibular second premolar, returning on the lingual side of the prosthetic plane, and finally capturing the buccal part of the prosthetic plane (Figure 2b). This protocol was named the \"RESCAN\" protocol. All subsequent scans obtained by this protocol were grouped in the \"RESCAN\" measured data group. 3. A third scan in which the first scan was imported, and the crown preparation interest area was trimmed and rescanned. The trimmed area consisted of the prepared left mandibular first molar, the mesial half of the distal neighboring tooth (left mandibular second molar), and the distal half of the mesial neighboring tooth (left mandibular second premolar). The rescanning path started distally on the left mandibular second molar and followed the occlusal plane until reaching the left mandibular second premolar, returning on the lingual side of the prosthetic plane, and finally capturing the buccal part of the prosthetic plane (Figure 2c). This protocol was named the \"DELETE&RESCAN\" protocol. All subsequent scans obtained by this protocol were grouped in the \"DELETE&RESCAN\" measured data group. The scanning scenarios were repeated 30 times following the same protocol, obtaining a total of 90 STL files consisting of three groups of 30 subjects each, representing the measured data for the in vitro part of the study.