Effects Of Different Surface Treatments On Bond Properties Of Porcelain Fused To Electroformed Copings

Technology of galvanoceramic is a process of fabricating ceramometal restorations utilizing 99.9% pure gold copings by electroforming techniques, electrodepositing a metal onto a suitable substrate in specific electroforming apparatus. It is used increasingly extensive in clinic since it came into China in 1990's because of excellent marginal fit and biological properties.Evaluation of the metal-ceramic bond strength is an important indicator of the restorations, it can reflect the strength and durability of restorations to some extent. The bonding between porcelain and metal including a combination of mechanical, chemical bonding, van der Waals force and compression bonding, but at present, the nature of the bonding has not been completely defined. It is believed to generally that conventional precious and base metals can produce strong chemical bonding with porcelain result from suitable oxidation of the metal. No research of the bonding between electroformed copings and ceramic has been reported at present.The purpose of this study was to evaluate the shear bond strength between porcelain and electroformed copings after different surface treatments, with comparison of Ni-Cr alloys, to explore the bonding mechanism through observing the electroformed coping surface and interface of metal-ceramic by SEM and EDS analysis. It will provide the basis for clinical application.Partâ… Effects of different surface treatments on bond strength of porcelain fused to eleetroformed copingsMaterials and Methods: Forty-five cylindrical Ni-Cr alloys were made, and gold copings were deposited on them and divided into 5 groups randomly. Different surface treatments were taken on round gold surface, including no treatment, 50μm Al₂O₃ sand blasting, 110μm Al₂O₃ sand blasting, gold bonder applying after 50μm Al₂O₃ sand blasting, gold bonder applying after 110μm Al₂O₃ sand blasting, and the same nine Ni-Cr alloys were cast as contrast, the gold copings and Ni-Cr alloys were both received two layers of opaque and two layers of body porcelain. Shear tests were performed in a universal testing machine. After loading the sections were examined by SEM and EDS analysis. The data were submitted to single-factor analysis of variance.Results: The mean shear bond strength values respectively were: 6.99 MPa, 9.04MPa, 9.80 MPa, 12.19 MPa, 12.86 MPa, significantly lower than that of Ni-Cr alloy 26.76 MPa. The one-way ANOVA show significant differences among the groups(p＜0.05). Fracture model and shear bond strength were not relevant. Conclusions: The shear bond strength between porcelain and electroformed copings are significantly lower than that of Ni-Cr alloy. The gold bonder and sand blasting can significantly improve the bond strength of porcelain fused electroformed pure gold copings.Partâ…¡Effects of different surface treatments on microstructure of porcelain fused to electroformed copings and metal-ceramic interfaceMaterials and Methods: Five electroformed copings were made in the size of 5 mm×5 mm, different surface treatments were taken respectively, including no treatment, 50μm Al₂O₃ sand blasting, 110μm Al₂O₃ sand blasting, preoxidation after 110μm Al₂O₃ sand blasting, gold bonder applying after 50μm Al₂O₃ sand blasting. Another two metal-ceramic specimens by electroforming were made in the size of 20 mm×5 mm(with and without gold bonder). The electroformed copings and interfacial area were examined by SEM and EDS analysis.Results: Surface roughness increased by sandblasting, O content had not been greatly improved by preoxidation, the coping surface formed a porous structure after applying gold bonder. The gold and porcelain combined tightly, mechanical chimera and simple diffusion of Al, O elements were observed in interfacial area.Conclusion: The gold bonder can increase mechanical bonding between porcelain and electroformed copings. The copings and porcelain combined tightly, simple elements diffusion was observed obviously in interfacial area.