Bond strength vs layer thickness. Layer thicknesses grouped into three classes. Material: unalloyed Titanium samples adhered together with Refobacin®-Palacos®R. Before adhering together, samples were pre-coated by a protecting layer out of PMMA and BisGMA, similar to the layer protecting the silica layer on surface of the artificial stem. Without/with hydrolytic load 30 to 360 days; demineralized water, 37°C.