In-vitro comparative study to evaluate bond strength of porcelain on metal sub-structure fabricated by selective laser melting (SLM) technique after application of different surface treatments

Introduction: Metal-ceramic bond strength is one of the essentials that must be studied due to recent develop-ments in dentistry. Objectives: This study aimed to evaluate the ceramic bond strength with metallic sub-structure made of chro-mium-cobalt alloy and fabricated by selective laser melting (SLM) technique after applying different surface treatments. Material and methods: 40 metallic strips of Co-Cr alloy manufactured by SLM technique were divided into two main groups, A and B, which were again divided into 4 sub-groups as follows: A1 – natural surface roughness maintained ( n = 10); A2 – natural roughness with a bonding agent application ( n = 10); B1 – sandblasted surface ( n = 10); B2 – sandblasted surface with a bonding agent application ( n = 10). A surface roughness measuring test was carried out to obtain Ra-Rz values. Three-point bending test according to ISO 9693 standards was performed to determine the metal-ceramic bond strength in MPa. Fracture failure mode was determined by using an optical microscope. Results: Student’s t -test was used to compare among the mean bond strengths of sub-groups, with a significant difference observed only between A1 and A2 and between A2 and B2 sub-groups. Mann-Whitney test was applied to compare among the mean ranks of the failure modes, with a significant difference noticed only between A1 and A2 sub-groups. Conclusions: The bond strength in all the studied sub-groups exceeded the required minimum 25 MPa, according to ISO 9693 standards. The bonding agent had a minor effect when applied on sandblasted surfaces, while it had an important effect when applied on a natural surface roughness.