| Nowdays, titanium and titanium alloys are widely used in dentistry and other medical fields due to their good corrosion resistance, excellent biocompatibility and superior mechanical properties, and also because of the higher prices of noble metals and much more concerns about biosecurity of nickel-containing metals, titanium and titanium alloys are widely considered likely to become to be substitute of metal ceramic restorations. Besides the esthetics, the excellent strength of PFT can avoid the risk of the the zirconia ceramic framework fracture caused by the excessive occlusal force in the posterior teeth region. Moreover, electrochemical corrosion between different metals can be avoided in oral environment. However, oxidation and phase transformation of pure titanium easily occur under high-temperature conditions, which leads to the insufficient durability of the Ti-ceramic bond and limits the clinical application of the PFT restorations. So most of the research in recent years are focused on how to control the formation of the oxide layer in sintering process, consequently numerous elements have been used as surface coatings to prevent excessive titanium oxidation during the firing stage. It has been reported that coating titanium surfaces with Si3N4、 SiO2、Cr and TiN lowers its rate of oxidation, similar results have been obtained by coating the titanium with gold paste and magnetron sputtering with gold ions. Though both the methods can prevent over-oxidation on the titanium surface and improve Ti-ceramic bond strength, but they are very sensitive to the clinical coating technique. Ionic self-assembled multilayer(ISAM) technique is a very new technology that can use electrostatic interactions between different ions to form a thin film, and the type of film base is unlimited, such as glass, silicon films, metal, etc. So this technique provides a new research idea for introducing a intermediate coating between titanium and ceramic.ObjectiveTo investigate the effect of composite nano-gold films deposited on the pure titanium by ionic self-assembled mutilayers (ISAM) technique on the adhesion of porcelain to titanium.MethodsTwenty pure titanium specimens were prepared by machining procedure in rectangular shape according to ISO 9693 to make two groups of each set (n=10). All specimens were sandblasted with 150 μm Al2O3 particles at the pressure of 0.2 MPa. Then one group of the specimens were deposited composite nano-gold films, and the other serve as a control group. A layer of porcelain was built up onto the titanium strips of both groups with a conventional technique. Field emission scanning electron microscope (FE-SEM) was used to observe the surface morphology of titanium specimen after depositing composite nano-gold films, and further observe the microstructure of the interface between titanium and porcelain after sintered. Optical Stereomicroscope was used to characterize the titanium-porcelains adhesion and determine the mode of failure after three-point bending test was performed. The distribution of the Au element on the interface of titanium-porcelain was detected by electron microprobe (EMP).ResultsThe adhesion of nano-gold film deposited group was significantly higher than those of the undeposited group [(36.24±3.64 MPa) and (30.78±3.83 MPa), p<0.05]. FE-SEM illustrated that the surface of the nano-gold deposited group formed a uniform, dense composite nano-gold film. Stereomicroscope and SEM images showed that composite nano-gold films enhanced the bond strength between porcelain and titanium. Small, white spots of gold particles could be detected along the titanium-porcelain bonding interface by electron microprobe (EMP).ConclusionsThe bending strength between porcelain and titanium was significantly improved when titanium was deposited with composite nano-gold films. |
PDF Full Text Request