Comparison of Mechanical and Surface Properties of 3D Printed and CAD-CAM Milled Resins for Interim Crowns - An In vitro Study

Abstract Context: For the success of the definitive restoration, interim prostheses are essential to maintain function in the complex environment of the oral cavity. Aim: The aim was to characterize the mechanical properties and the surface of interim restoration material fabricated for fixed dental prostheses using two digital methods. Materials and Methods: Specimens were fabricated with computer-aided design and computer-aided manufacturing (CAD-CAM), milled polymethyl methacrylate (PMMA), and three-dimensional (3D) printed resin. The topography, roughness, and Vickers hardness number (VHN) of polished and unpolished surfaces were evaluated. The cement film was observed with confocal microscopy. The flexural strength and maximum force at fracture of cemented molar single-unit crowns were determined. Statistical Analysis: The mean values of the groups were analyzed by using the Shapiro-Wilk test and 1-way analysis of variance ( α = 0.05). Results: In both techniques, no statistically significant differences were found in the VHN ( P > 0.05); the roughness values of the unpolished surface increased significantly ( P = 0.002). The topographic information showed that CAD-CAM milled PMMA and 3D printed resin had a smooth surface after polishing, and a cement film was observed on all the walls of the abutment surface. The flexural strength ( P = 0.001) and the mean maximum failure load ( P = 0.002) were significantly higher for CAD-CAM milled PMMA. The failure of CAD-CAM milled PMMA crowns was classified as minimal fracture; for the 3D printed resin crowns, the fracture was through the midline. Conclusion: Both techniques provided clinically acceptable surfaces. CAD-CAM milled PMMA exhibited significantly higher failure at maximum load than 3D printed resin.