# Accuracy of 3D-Printed Master Cast Workflow Using a Digital Light Processing Primer
## Materials and Methods
Digital Workflow  
Cast Preparation and Scan  
The reference all-ceramic cast was scanned ten times by an intraoral scanner (Primescan, Sirona Dental Systems GmbH, Bensheim, Germany) using the Cerec 5.2.2 RC 1 software. The scanning path described by [PERSON] et al. [PERSON] et al. (2018) was applied by one operator in a darkened room. In the acquisition phase, each cast was trimmed so that the teeth and the alveolar ridge representing the keratinized gingiva were kept. In the model phase, the cast was shown after calculation by the scanning software with its base. This solid cast was carved out from the bottom to reduce material. The virtual casts were exported as system-specific 'cam' files and imported into the inLab CAM software (software 22.1 Beta 1, Sirona Dental Systems GmbH, Bensheim, Germany). For the printing device, Primerprint (Sirona Dental Systems GmbH, Bensheim, Germany) was chosen. The support structures were defined, and the printing process was initiated. The default parameters which included the number and position of the support structures with a spherical support tip were confirmed. Optimized quality was selected as an orientation strategy on the building platform. The detail quality \"very high\" for printing was chosen. For the polymer, a specific resin (Primeprint Model, Sirona Dental Systems GmbH, Bensheim, Germany) was used. Two casts were arranged automatically and printed at the same time. After printing, post processing was performed by the post processing unit (Primeprint PPU, Sirona Dental Systems GmbH, Bensheim, Germany) to remove uncured resin by rinsing the specimens and for final resin polymerization. After completing the job, the support structures were removed. The casts were digitized with the same aforementioned ILS, and the files were provided as stl files. Printing parameters can be found in Table 1.  
Available Data Files for Surface Comparison by Superimposition  
Five ILS scans of the ceramic reference cast served for the precision analysis of the ILS reference scanner. To analyze the conventional and digital cast fabrication, one randomly selected stl file of the digitized reference cast [REF], the ten stl files of the scanned gypsum casts [CON], and the ten stl files of scanned printed casts [PRINT] were available. Additionally, the ten intraoral scans [IOS] within the digital print workflow were exported as stl files for analysis. All superimpositions were performed in GOM Inspect Suite 2020. Trueness  
For full-arch trueness evaluation the combinations of [REF]-[CON], [REF]-[PRINT], [REF]-[IOS] and [IOS]-[PRINT] were available. For test combinations involving [REF], [REF] was defined as a reference object for surface combination while [CON], [PRINT] and [IOS] were the test objects. According to the definition of trueness testing, only one [REF] data file served as reference and was tested against ten [CON], [PRINT], and [IOS] files each. Unlike the actual definition of trueness testing, within the surface comparisons [IOS]-[PRINT], the [IOS] files were set as reference objects. Each of the ten [IOS] files was superimposed with its corresponding [PRINT] file. All test objects were superimposed with the reference object in one coordinate system via global best-fit alignment. To avoid the inclusion of outliers, the meshes of all test casts were cut interdentally, and all parts of the gingiva were cut out (Figure 2b).