Effect Of Functional Gradient Coating Formed By Magnetron Sputtering On The Bonding Between Pocerlain And Pure Titanium

Titanium has been applied to dental implants, denture casting frame and crown and fixed bridge dentures because of its excellent biocompatibility, good Corrosion resistance, ideal physical and mechanical properties and relatively low price. However, as Titanium and Porcelain bonding is weaker than that of the precious metals and base metals in traditional porcelain system, Titanium Porcelain restorations is limited in a wide range of clinical applications. At present there are two points of views explaining why the current Titanium - Porcelain bonding is weak: the first is in the high temperature of ceramic sintering and in titanium surface there appears a layer of thick and loose oxide film which lacks of porous adhesive force, the second is the mismatch of thermal expansion coefficient between Titanium and Porcelain.Object: In this study, we apply magnetron sputtering to build two single-layer nitride coating (Si₃N₄ coatings and coating ZrSiN), and two types of gradient coatings (Gradient coating ZrSiN and Si/Si₃N₄/ZrSiN) respectively in the surface of pure titanium in order to control the over-oxidation of Titanium surface in high-temperature conditions, to reduce the mismatch of thermal expansion coefficient between Titanium and Porcelain, and to "buffer" thermal stress.Methods: The coating was formed by Magnetron Sputtering; scanning electron microscope (SEM)and Energy Dispersive Spectrometer (EDS) were used to observe the morphology and composition of coating; Auger Electron Spectroscopy (AES) was also used to analyze the change of element contribution in gradient coating;the bond-strength of titianium-ceramics was examined by three-point bending test.Result: we could see two nitride single-layer coating (Si₃N₄ coatings and coating ZrSiN) and two types of gradient coatings (Gradient coating ZrSiN and Si/Si₃N₄/ZrSiN) formed by magnetron sputtering in the scanning electron microscope. The Si₃N₄ coatings ZrSiN formed by magnetron sputtering appeared as a layered film, with sparse small pore, the two coatings not complete and homogeneous. Titanium-ceramic bond strength combined with three-point bending test shows that the two single-layer nitride coatings (Si₃N₄ coatings and coating ZrSiN)and ZrSiN gradient coatings can significantly improve the Titanium-ceramic bonding strength(P<0.05)with no significant difference between two nitride single-layer coating(P>0.05.). The gradient coating of high Si content ZrSiN is higher than low Si content ZrSiN (P<0.05).low N content Si/Si₃N₄/ZrSiN gradient coating can promote the Titanium-ceramic bonding strength(P>0.05).There is not significant difference between High N content Si/Si₃N₄/ZrSiN gradient coating and control group(P>0.05). Electron microscopy and energy spectrum analysis shows that the two single-layer nitride coatings can effectively block the proliferation of the surface of titanium oxide. The failure mode between the ZrSiN gradient of the ceramic coating of titanium is the mixed failure of internal ceramics and internal oxide. Failure mode between the ZrSiN gradient of the ceramic coating of Titanium is the mixed failure of the internal ceramics and internal coating. Auger electron spectroscopy analysis proves that N element distribution in ZrSiN gradient coating and Si element distribution in Si/Si₃N₄/ZrSiN gradient coating emerge gradient changes.Conclusion: Both two single-layer nitride coating (Si₃N₄ coatings and coating ZrSiN )and ZrSiN gradient coating with different Si content can promote the bonding of Ti-porcelain.Although low N content Si/Si₃N₄/ZrSiN gradient coating can improve the bonding of Ti-porcelain ,the coating is not benefit for porcelain fused to titanium. high N content Si/Si₃N₄/ZrSiN gradient coating can't improve the bonding of Ti-porcelain.