Objective To investigate the effects of the improved FUS- invest investment for zirconium- oxide titanium crown and bridge on the reaction layer. Methods 10 mm×10 mm×1 mm titanium castings were invested. Spectrum analysis was done to its reaction layer, the metallographic examination was observed and Vickers hardness was measured. Results The reaction layer was not obvious by the metallographic examination. The layer with plenty of Si was hardly detectable. The needle crystal layer diffused distribution on the surface of the titanium matrix. The depth was about 55 μm. Spectrum analysis showed that the contents of Si and Zr decreased as the depth increased. The microhardness, which obviously decreased from the surface to the matrix, tended to be equal with the hardness of the matrix after the depth reached 75 μm from the surface. Conclusion The thickness of the reaction layer of the improved FUS- invest investment for zirconium- oxide titanium crown and bridge was decreased to 55 μm from 85 μm, which was the thickness before improvement.
