Experimental and FEM investigation of adhesion strength of dental ceramic to milled and SLM fabricated Ti6Al4V alloy

The aim of the present paper is to investigate the adhesion strength of dental ceramic to milled and selective laser melted (SLM) Ti6Al4V alloy by experiment and finite element method (FEM). The experimental study was done by three-point bending test. Before applying the porcelain, the metal surface was treated by sandblasting, application of bonding agent and a combination of sandblasting and bonding layer. The novelty is that FEM simulations of individual samples from each group were conducted using the experimental load-strain graphs. The normal, tangential and equivalent von Mises stresses at endpoint of the edge of porcelain coating and bonding agent sublayer were determined. It was found that the distribution of the equivalent stresses along the porcelain edge on the porcelain/metal interface is uneven: low stresses at both ends and maximum value in the central part. The Y-axis normal stresses, acting perpendicular to the porcelain/metal, bond/metal, or porcelain/bond interface, have greatest values which is primary reason the coating to be adhesively delaminated by peeling the porcelain off the metal or bonding agent. For the milled specimens, the stress trend follows the adhesion strength trend. In the combined treatment, the highest equivalent and normal stresses are generated in the bond sub-layer. If they are higher than the cohesive strength of the ceramic, the porcelain coating is destroyed cohesively by cracking. For the SLM fabricated specimens, the bond treatment increased the stresses at the bond/metal interface, and the stresses at the bond/porcelain interface were commensurate with the experimental adhesion strength. This causes the destruction of the coating to occur by peeling the porcelain off the bonding agent.