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Effect of Firing Temperature on the Metal to Ceramic Bond Strength of a Porcelain Fused to Metal Restoration of a Co-Cr Alloy by Means of Selective Laser Melting (SLM)
S. Zhang, D-W. Yushu, B-X. Liu, B. Sun, C-Z. Yan, L. Hao, Q-S. Wei and Y-S. Shi

Metal to ceramic bond strength is a critical issue in porcelain fused to metal restoration. This study investigated the effect of firing temperature on the metal to ceramic bond strength of porcelain fused to metal restoration of a Co–Cr alloy fabricated by selective laser melting (SLM). The specimens were fused to porcelain according to ISO 9693:1999 standard at the firing temperature that is increased from 915 to 935°C by a step size of 5°C. Three-point bending tests were carried out to measure the bond strengths. The results show that the maximum bond strength is 49.2 MPa at the firing temperature of 930°C for the SLM porcelain fused to metal restoration. Scanning electron microscope (SEM) analysis indicates that protruding structure formed in SLM process enhances bond strength by forming mechanical locking structure. Energy dispersive X-ray spectroscopy indicates that the firing temperature influences bond strength by changing the interfacial bond thickness. At the optimum firing temperature of 930°C, the largest thickness is about 2.0 μm. This findings shows that the SLM metal to ceramic system exhibited a bond strength that can meet the requirement of ISO 9693:1999(E).

Keywords: Fibre laser, selective laser melting (SLM), Co-Cr alloy, powder, porcelain fused to metal restoration, firing temperature, metal to ceramic, bond strength

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