ADHESION STRENGTH EVALUATION OF CERAMIC COATINGS ON CAST AND SELECTIVE LASER MELTED Co-Cr DENTAL ALLOYS USING TENSILE SPECIMENS

  • 1 Faculty of Dental Medicine, Medical University of Varna, Varna, Bulgaria
  • 2 Pisarenko Institute for Problems of Strength, Nat. Ac. Sci. of Ukraine, Kiev, Ukraine
  • 3 Medical College, Medical University of Varna, Varna, Bulgaria

Abstract

Studying the fracture characteristics of porcelain coatings plays a main role in selection of materials for metal-ceramic restorations. The aim of this work is to study the effect of the substrate manufacturing process on the adherence of the porcelain. The coatings of porcelain IPS.Inline (Ivoclar Vivadent) are fused onto dental Co-Cr alloys fabricated via casting (Biosil F) and Selective Laser Melting (SLM) (Co212-f). The adhesion strength of the ceramic coatings is studied under tensile load of flat specimens. The interfacial shear strength is determined using experimental results. The shear stress distributions in the metal-ceramic interface at the critical load are evaluated by analytical approach. It is established that the interfacial shear strength values of ceramic coating are 67.5 MPa for cast Biosil F alloy and 83.8 MPa for SLM Co212-f alloy. The higher shear strength of the porcelain to the SLM samples is due to the nearly two times higher surface roughness, which is reason for increasing both the mechanical and the chemical adhesion. The nature of the fracture of the ceramic coating on the Co-Cr alloys, produced by casting and SLM, is similar and is mixed adhesive–cohesive mode. The higher adhesion strength of the porcelain coating to the SLM dental alloy is a good precondition for the SLM application in production of metal-ceramic fixed partial dentures for areas with heavy loads.

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