In addition, the energy-spectrum scanning picture of every single element was illustrated in Figure 5. The element content of Zr in the outer side of zirconia substrate (Area A) was 78.78 wt%, and was slightly reduced to 74.96 wt% in the bonding interface (Area C). Besides, Zr contents were detected to be 12.19 wt% and 3.89% in the bonding porcelain layer (Area D) and the veneering porcelain layer (Area E), respectively. The element content of Si in the veneering porcelain layer (Area E) was 43.03%, and it decreased to be 39.21% in the bonding porcelain layer (Area D). Besides, small amounts of element Si were detected both in the bonding interface (Area C) and zirconia substrate (Areas A and B), indicating the diffusion of Si occurred in the zirconia matrix after pre-sintering process. The chemical bonding was confirmed by element diffusion phenomenon, and it was beneficial in the increasing of bonding strength between zirconia and veneering porcelain.