## 2 Materials and Methods
### Thermomechanical Aging  
An experienced operator (M.E.G.) scanned the entire anatomy of the crowns in a temperature and humidity-controlled room under ambient light using the same intraoral scanner used to digitize the prefabricated abutment. The intraoral scanner was calibrated before starting the scans and recalibrated in every 5 crowns, and the operator took 5 min breaks after every 5 crowns to minimize fatigue-related deviations. The scans were checked for any error and saved as before thermomechanical aging test STL (BTMA-STL) files to further compare them with after thermomechanical aging STLs (ATMA-STLs) to evaluate external surface deviations and occlusal surface wear. The crowns were randomly (Excel; Microsoft Corp, Seattle, WA, USA) mounted on a dual-axis computer-controlled mastication simulator (Dent Ar-Ge; Analitik Medical, Istanbul, Turkey), including a thermal-cycler. Crowns were aged at 1.7 Hz frequency for 1.2 million cycles under 50 N load with a lateral movement of 1 mm and a vertical and lateral sliding speed of 60 mm/s to simulate 5 years of functional loading [4; 15; 16; 17]. The load was applied with 3 mm stainless steel sphere antagonists, which contacted the central fossae of the crowns. Force concentrations at asperities on the occlusal surface were avoided by placing a piece of tin foil between the crown and the steel sphere. Crowns were also simultaneously thermocycled for 6000 cycles between 5-55 \({}^{\circ}\)C with 30 s holding and 15 s transfer time in distilled water. After thermomechanical aging, crowns were visually inspected in a stereomicroscope (SMZ 1500; Nikon Corp., Tokyo, Japan) for the presence of any failures (Figure 2). Thereafter, crowns were scanned within 48 h with the same intraoral scanner to generate ATMA-STLs. To evaluate the dimensional stability, which refers to the surface topography (external surface changes in RMS) and linear changes (mesiodistal width in microns) against liquid media storage and loading, and occlusal surface wear, which refers to the volume loss against liquid media storage and direct contact with the stainless sphere load application, of the crowns, an industrial-grade 3-dimensional (3D) quality control and dimensional inspection software program (Geomagic Control X v.2022.1; 3D Systems, Rock Hill, SC, USA) was used. For each specimen, BTMA-STLs were imported as the reference data. Then, ATMA-STLs of corresponding crown were imported and superimposed over BTMA-STL using initial alignment followed by best-fit alignment to minimize errors. Root mean square (RMS) method was used to calculate the 3D deviations at the external surfaces. The \"3D Compare Tool\" of the software was used to generate color maps for the quantitative evaluation of the deviations at the external surfaces. Overcontoured areas are indicated in red color, and undercontoured areas are indicated in blue color, with maximum/minimum  
Figure 2: Occlusal wear of tested materials after thermomechanical aging. Blue arrows indicate area of wear, while bottom images show cross-sectional view of worn areas. MS, Crowntec; GR, G-CAM; PMMA, breCAM.monoCOM; BC, Brilliant Crios. deviation values set at 100 \(\upmu\)m. The tolerance range was set at 10 \(\upmu\)m and indicated in green color. To measure the mesiodistal width deviations, BTMA-STL and ATMA-STL were superimposed as mentioned above, and one coordinate measuring machine (CMM) point was generated on the mesial and the distal contact surface on the superimposed data (Figure 3). These CMM points ensured the greatest mesiodistal width on the occlusal third, and the distance between these points was automatically calculated for both STLs. The absolute difference between these values was used for the statistical analyses. To calculate the volume loss, ATMA-STLs were superimposed over their respective BTMA-STLs, and the \"measurement tool-volume inspection tool-enclosed volume\" feature of the software was used to encapsulate the worn area.