DESIGN AND FABRICATION OF DENTAL CROWNS USING SELECTIVE LASER SINTERING

Abstract

Additive Manufacturing (AM) represent a novel category of manufacturing technologies characterized by the layered production of objects. They emerged in the 1980s with the introduction of the first 3D printer, operating on the principles of stereolithography. Since their inception, AM has experienced rapid advancement, leading to the development of a diverse range of technological processes compatible with various materials such as polymers, composites, ceramics, pure metals, and alloys. One of such technology is the SLS, which is capable of printing metal and ceramic parts. This capability to create personalized structures with intricate shapes has particularly driven the initial applications of AM in dental medicine. This study explores the behavior of dental bridges fabricated from Co-Cr alloys using selective laser sintering (SLS) additive technology. Through simulation analysis and customized three-point bending tests on four types of fixed partial dentures, the study investigates the influence of connector cross-sectional shapes on bending fracture. Simulation analysis reveals stress distribution and deformation, guiding the selection of optimal bridge designs for experimental testing. The highest equivalent stresses concentrate at the junction of the connector and crown wall of the 2nd premolar, indicating potential failure locations. Bending tests validate the simulation results, with all bridges fracturing at the 2nd premolar crown connector. The trapezoidal connector bridge exhibits the highest load capacity, followed by square, elliptical, and random connector models. Fracture analysis reveals a mixed-mode fracture pattern, with distinct tensile and shearing fracture areas. SEM analysis highlights striations and grooves indicative of shearing fracture, and dimples and peaks suggesting tensile fracture. Tensile fractures initiate at the inner surface of the 2nd premolar crown, forming conical craters whose size correlates with maximum load capacity. The trapezoidal connector bridge exhibits the largest tensile fracture area and crater, while the random connector type shows a larger proportion of shiny fracture surface, indicating lower resistance to tensile load. These findings provide insights into the mechanical behavior of SLM-printed dental bridges and inform the design optimization for enhanced load-bearing capacity, fracture resistance and longer life.