| Titanium has been applied increasingly in prosthodontics. However,bond strength of titanium-ceramic system is weaker than bond strength of traditional metal-ceramic system, so its application is limited. The reasons for weak bond between titanium and ceramic are titanium characteristics of strong reaction with oxide and mismatch of thermal expansion coefficient between titanium and porcelain. For those reasons, titanium porcelains with low fused temperature and low TEC are introduced by major porcelain manufacturers to solve the problem of titanium-ceramic bond. Comparing with traditional ceramic system, bond agent is first introduced into titanium porcelain system. In the system, bond agent is directly fused to the surface of titanium and becomes an important factor of titanium-ceramic bond. But there are many controversies on effect of bond agent. Micro-arc oxidation is a technology which can form ceramic oxide film on the surface of titanium. The film has metallurgical bonding with titanium and strong bonding with substrate. The dense inner layer of film could prevent the process of continued oxide reaction of titanium, while the porous outer layer could increase the contact area with the ceramic. At the same time, the characteristics and compositions of film could be changed by adjusting the electrolyte to enhance the chemical bond between titanium and ceramic, so the film would be a ideal middle layer. But these studies almost focus on MAO parameter adjustment. The process of titanium-ceramic bonding is a result of interaction between titanium and ceramic. Recently, there is large difference between titanium porcelains in market, so it is important to choose the titanium porcelain which is fit to MAO. It needs further study.In this paper, the study of bond agent combines with MAO. Through comparison of the effect of different brands bond agents, the effect of different bond agents and its mechanism are discussed. At the same time, we observed the effect of bond agents on titanium-ceramic bonding after MAO and select the titanium porcelain which is suitable for MAO.Objective: To study the effect of different bond agent on titanium-ceramic system and its mechanism. To analyze the effect of bond agent after MAO and select the titanium porcelain which is suitable for MAO.Methods: In this experiment, we choose three brands titanium porcelains including Super porcelain Ti22(Noritake Japan),Duceratin Kiss(Dentsply American),Titankeramik(Vita Germany). These titanium porcelains have good representation because they are the important products of major manufactures. Using SEM/EDS to analyze the morphology and chemical composition, we evaluate basic physical and chemical properties of titanium porcelain. The sandblasted pure titanium specimens are applied respectively three kinds of titanium porcelains. Each porcelain group is further divided into two subgroups: with bond agent group and without bond agent group. According to ISO9693, 3-point bending test is used to evaluate bond strength of titanium-ceramic system. SEM/EDS are used to observe the interface and separate surface of titanium-ceramic system and oxygen diffusion range. Combining the chemical composition of bond agent, we analyze the effect and mechanism of bond agent on titanium-ceramic system. Titanium specimens are treated by MAO. Electrolyte is made of the deionized water and Na2SiO3 20g/l﹑NaOH 2g/l. The interface of titanium-ceramic system and oxygen diffusion range are investigated by SEM/EDS to analyze the effect of bond agent and to select titanium porcelain which is suitable for MAO.Results: Through observing morphology of bond agent, we find that particle size distributions of bond agent are uneven. In the bond agent powders, there exist some large particles with dimension of dozens microns and small particles which dimension is only a few microns. According to the result of EDS, it is showed that all of the three bond agents are SiO2-based and mixed with a variety of metal oxides. But there are large differences in the compositions of metal oxides and weight percent of the same metal oxide.According to results of bond strength of specimens after sandblasting treatment, we find that bond agents of Super Ti22 and Duceratin Kiss could improve significantly titanium-ceramic bonding. While Titankeramik with bond agent show a little higher bond strength than that without bond agent, but showing no statistical difference. These results demonstrate that the three bond agents have beneficial effects on titanium-ceramic bonding to different degrees. According to SEM/EDS result of interface of titanium-ceramic system, impact interfaces are found in the Super Ti22 and Duceratin Kiss with bond agent groups and the oxygen curves decline rapidly after crossing the titanium-ceramic interfaces, indicating the two bond agents have good wettability and can effectively control the oxygen diffusing into titanium substrate. However there are visible cracks and pores at the interfaces of other groups. The oxygen content curve of rest groups decline slowly, indicating that thicker oxide layers are formed at the surface of titanium substrate compared with Super Ti22 and Duceratin Kiss with bond agent. The difference in chemical composition of three bond agents indicate that different chemical bonding is formed at the interface of different bond agents and titanium.When titanium specimens are treated by MAO, bond agents of Super Ti22 and Duceratin Kiss could still improve significantly the bond strength of titanium-ceramic system. However, Titankeramik with bond agent group just show a little higher bond strength than without bond agent group, but showing no statistical difference. These results demonstrate that the three bond agents still have beneficial effects on titanium-ceramic bonding to different degrees after MAO. Comparing to other two titanium porcelains, Super Ti22 show better bonding characteristics, which indicate that it is more suitable for MAO. By observing interface of titanium-ceramic system, the interfaces have been improved significantly. Just a little cracks and pores could been found at the interfaces of Titankeramik with bond agent group and without bond agent group. According to the results of elemental line scanning, oxygen diffusion has been controlled in the Super Ti22 and Duceratin Kiss with bond agent groups after MAO.Conclusions: There exist large difference in chemical compositions among the three bond agents, which indicate that there might be large different in property of bond agents. The three bond agents can improve titanium-ceramic bond to different degrees. The degree of improvement should been affected by the wettability and chemical bonding of bond agent. The bond agent could still enhance titanium-ceramic bonding after MAO. The titanium specimens treated by MAO show strong bonding with Super Ti22, which indicate Super Ti22 is more suitable for MAO than other two titanium porcelain.
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