Study On The Interface Behavior For The Porcelain Fused To Ni-Cr Alloy

Porcelain fused to metal(PFM)have the virtue of metallic obdurability andimpact resistance,ceramic wear resistance and corrosion resistance .And inaesthetic property,biocompatibility and other aspect ,it has predominant behave .Ithas been a perfect restoration of dental prosthesis since the clinical applicationin 1950s .The Ni-Cr alloy is cheap,its elasticity and strength is high ,it can makethe repair body of the tooth thinner, so the natural tooth can not be burnish somuch. Therefore it is very important in PFM in our country. The metal alloy ofNi-Cr already has been used for 3 or 4 decades, but the collapse porcelain andcrack porcelain of porcelain fused of Ni-Cr alloy is still accounted for 59.1% ofthe whole clinical defeat case.The paper aims at existent problem in the clinical application of PFM, analyzesclinic defeat case, studies in depth the influence regulation of technologicalparameter to PFM interface microstructure and property, synthetically considerscoefficient of thermal expansion and biocompatibility of material, surfacesputtering Ti buffer layer to Ni-Cr alloy, studies the influence mechanism of Tibuffer layer to PFM, makes a primary study of interface behavior mechanism forPFM.Conclusion have been drawn as follows: (1) There is crack, pores, impurity andpipes in PFM. The cracks is the main cause of collapse porcelain and crackporcelain , these defects are relevant to the structural design of PFM, technologyand residual stress in PFM, the diversity between coefficient of thermal expansionof Ni-Cr alloy and porcelain makes greater residual stress in process ofrefrigeration.(2) The shear bond strength of porcelain to Ni-Cr alloy is 37.52MPa withfiring-temperature T=990℃ ,firing time t= 1.0min,vacuum =50hpa, compare tofiring temperature T=900℃ ,shear bond strength improves near 4 times,there islittle influence to shear bond strength in further improvementfiring-temperature.Low firing-temperature,mutation interface of metal-porcelain ,low bond strength;raising firing-temperature,interface of metal-porcelaintranslating from mutation to compound type, and the bond strength increasing .(3) The shear bond strength presents a aggrandizement trend along 0.5minfiring-time to 10min firing-time with firing-temperature T=990℃ ,vacuum=50hpa.The shear bond strength is 42.7MPa at 2.5min firing-time, compared with 0.5minfiring-time, the shear bond strength increases more than 3 times. If increasingfiring-time further, the shear bond strength of PFM interface will falls in evidence.(4) Porcelain fused to Ni-Cr alloy at Vacuum from 50hpa to 100hpa withfiring-temperature T=990℃ , firing-time t=2.5min Interface of Ni-Cralloy-porcelain have many pores and microcracks, the bond strength is low.(5) The interface of porcelain fused to Ni-Cr alloy was smooth, reaction layerwas obviously formed. A new chemical compound reaction layer was examined inthe interface, in virtue of interaction of in porcelain-metal interface between Ni-Cralloy and glass-phase fused porcelain. The metallurgical bond between Ni-Cralloy and porcelain was effectively improved, the interface defects were reduced,the good bonding between Ni-Cr alloy and porcelain was realized.(6) Porcelain fused to Ni-Cr with the surface sputtering Ti, TiO2 was examinedin the interface, it makes electron structure of interface present continuity, formsion key and covalence key ,plays a transition layer between Ni-Cr alloy andporcelain, increases the interface bond strength of PFM.