Abstract
Objectives: This research aims to investigate the impact of laser angulation (0-, 45- and 90-degree) on a direct metal laser sintered Cobalt Chrome partial denture frameworks alloy on its mechanical properties.
Methods: Specimens (n=10) where produced using stereolithographic (STL) models in accordance with American Society for Testing and Materials testing standard E8/E8M. Manufacturing of the specimens was done using a Direct Metal Laser Sintered additive manufacturing machine (Prox DMP 200 Dental, 3D Systems, France). Specimens were fabricated using three different laser angulations (0-, 45- and 90-degree). Tensile testing was carried out to assess, yield strength (RP0.2, MPa), elongation (%) at failure, and ultimate tensile strength (GPa). Specimens were loaded in tension, using a 50KN load cell, at a loading rate of 1mm/min, until fracture on a universal testing machine (Instron 3369, Norwood, Massachusetts, USA). Scanning electron microscope images were utilized to analyze fracture surfaces of selected specimens post failure. Nanoindentation was used to determine, hardness and elastic modulus, using one cubic specimen for each build orientation, at a static load of 200mN with 35 indents at the interfacial surface layer.
Results: The 45-degree angulation resulted in the lowest elastic modulus of 213.3GPa and highest tensile strength of 1180.9MPa. The 90-degree angulation resulted in the highest elongation of 10.6%. and highest hardness of 7.0GPa. The SEM of the fracture surfaces for the three different build angles were comparable, with irregular fracture patterns. Semi-melt areas were identified in all groups, and different fracture topography was observed between the groups.
Conclusions: CoCr dental alloy manufactured using DMLS produced favorable results with regards to its mechanical properties. The 45-degree build angulation resulted in the highest mean yield strength and featured a high tensile strength and a proportional lower elongation%. The SEM images suggest that the laser angle has an impact on the mechanical properties.