## 2 Materials and Methods
### Specim Fabrication Technique  
**Conventional technique**. One crown fabricated with the CAD-CAM technique was secured on the prepared cast, and a silicone impression using light and putty PVS impression material (3M Express Putty, 3M ESPE, MN USA) was recorded to form a mold to make interim crowns using the conventional technique. Two location grooves were placed on the buccal and lingual surface of the master model to replicate the positioning of the mold. The prepared teeth surface on the models were layered with a 0.1 mm layer  
Figure 1: Brief study methodology. of die spacer (Durolan die spacer, DFS Diamon, Shanghai, China). The prepared stone model was covered with a thin layer of petroleum jelly (Vaseline, Janssen, Surrey, UK) and thinned with air under pressure. An auto polymerizing resin material (Jet Tooth Shade(tm) Self-Curing Acrylic Resin 6/1 Kit, Lang Dental Manufacturing Co Inc., MN, USA) was mixed according to the instructions from the manufacturer and poured into the impression mold with a powder/liquid ratio of 1 gm/0.5 mL. The model was immediately seated in the impression mold with firm force and secured with bands. The resin was allowed to polymerize for 10 min and placed in a warm water bath at 55 \({}^{\circ}\)C for 10 min. The mold was separated carefully from the model without damaging the restoration. Excess material was removed, and the final interim restoration was finished (slow speed airotor and carbide bur) and polished (pumice). Ten crowns were fabricated using the above-mentioned technique (\(n=10\)). A metal mold of 10 mm diameter and 3 mm thickness was prepared. An auto polymerizing resin material (Jet Tooth Shade(tm) Self-Curing Acrylic Resin, 6/1 Kit, Lang Dental Manufacturing Co Inc) was mixed according to the instructions from the manufacturer and poured into the metal mold. The resin was allowed to polymerize for 10 min and placed in a warm water bath at 55 \({}^{\circ}\)C for 10 min. The mold was separated carefully from the disc without damage. Twenty disc specimens were fabricated using the above-mentioned technique. **CAD-CAM. ** Ten interim crowns were fabricated using the CAD-CAM technique (\(n=10\)). The prepared master die was scanned (S 50 Zenotec CAD; Wieland Dental, Pforzheim, Germany) to produce a model specimen for the prepared molar. The interim crown was designed using a software program (AUTODESK FUSION 360, Kilsyth, Victoria, Australia) with standard occlusal anatomy and contours. The prepared design of the scan and the interim crown were stored as an STL file. The PMMA prefabricated blocks (Cercon base PMMA blocks; DeguDent GmbH, Hanau, Germany) in shade A1 were milled using a wet CAD-CAM milling machine (Versamill; Axsys Dental Solutions, Wixom, MI, USA). The parameters were adjusted accordingly: 5 axes; 6.0 mm shaft tool; 60,000 rpm spindle. The milling machine noted that all the prescribed parameters were delivered accurately using a CAD-CAM PMMA block (Cercon base PMMA blocks; DeguDent GmbH, Hanau, Germany). For surface wear and roughness assessment, ten discs, each with a 10 mm diameter and 3 mm thickness, were fabricated using the CAD-CAM system (AUTODESK FUSION 360, Kilsyth, Victoria, Australia). The discs were designed, and the PMMA prefabricated blocks (Cercon base PMMA blocks; DeguDent GmbH, Hanau, Germany) in shade A1 were milled using a wet CAD/CAM milling machine (Versamill; Axsys Dental Solutions, Wixom, MI, USA). **3D Printing. ** For designing and fabricating 3D printed interims, a stereolithography-based 3D printer (MiiCraft 125; MiiCraft, Jena, Germany) was employed with a light-cure biocompatible resin (Freeprint Temp; DETAX GmbH & Co. KG, Ettlingen, Germany). The printer settings were adjusted accordingly: 50 \(\upmu\)m layer thickness, 405 nm wavelength, shade A1, curing time of 2.40 s per layer, and orientation at zero. Ten interim crowns and 30 FPDs (2 \(\times\) 2, 3 \(\times\) 3, and 4 \(\times\) 4 mm) were fabricated using the STL file created using CAD-CAM software (as explained in a previous section) and the 3D printer.