Impedance Study of the Electrochemical Systems:Endodontic Treatment and Bimetallic Thin-Film Corrosion
Date Issued
2007
Date
2007
Author(s)
Huang, Jui-Hsiung
DOI
en-US
Abstract
The electrochemical systems concerning endodontic treatment and bimetallic thin-film corrosion have been investigated in this study. Chapters 2 and 3 mainly deal with electrochemical impedance with nonfaradaic process for endodontic treatment. Two important cell-factors about electrolytic conductivity and geometry of the simulated canal system have been considered for impedance distribution of this dental system. The electrochemical characteristics and faradaic process of Mo/Al double thin-film in solution have also been investigated in this study and described in chapter 4.
Electronic apex locators (EALs) have been widely used in the dental treatment, and it is important to study the impedance characteristics of the root canal system. The study of impedance characteristics of the endodontic treatment with various electrolytes have been described in chapter 2, in which the in-vitro impedance measurements of root canals were performed and then used for the build-up of lumped equivalent-circuit model to the complicated anatomy of human tooth. The new proposed equivalent-circuit model fits the experimental results well compared with other models proposed previously by other researchers. Based on this new proposed equivalent-circuit model, the experimental results can be explained reasonably and the effect of electrolytes filling the canal is clearly understood. In addition to well-known index of impedance quotient in the literature, it has been found that the variation ratio method, SQ, can be employed as a significant indication of apex position, in which it can overcome the interference of electrolyte in canals more effectively. The values of variation ratios are below 0.05 at the apex and over-apex region for any electrolyte in the canal. Various impedance behaviors could be figured out from values of modified impedance quotient, Q. Furthermore, a typical theoretical model has also been set up for the root canal system to help explain the electric mechanism of root canal. It has shown that the principle of impedance quotient is valid for the elimination of electrolytic effect.
The apical size, especially for wide-open apex is now a crucial effect hampering the precision of EALs. As described in chapter 3, it has been found from in-vitro experiments that total impedance of the canal system decreased with enlarged apical diameter. The gradient change in impedance quotient would be less sharp with enlarged apical diameter, which may result in the inaccurate measurement of apex position to be obtained. Accordingly, the impedance quotient is not good enough to offer a good indication of apical endpoint for larger apical size. To overcome this apex size effect for the application of EAL, a novel apex indication, capacitance-base impedance correction, has been proposed based on three frequency measurements. By the in-vitro experiments of blocks and extracted teeth, it has been found that it is valid for the capacitance-base impedance correction for eliminating the apical size effect. For theoretical analysis, the model of a constrictive system with semi-infinite medium, which simulated the anatomy of tooth, has been proposed based on the electric behaviors of the disk electrode and geometrically constrictive resistance. From the simulated results, it indicated that the impedance quotient would be seriously restricted by apical constriction or size, whereas the capacitance-base impedance correction number was independent of that. The simulation results are in good agreement with that of in-vitro experiments. It would be helpful to understand the complicated mechanism of the human canal system as well as to improve the accuracy of the clinically dental applications.
The double thin-film structure of molybdenum (Mo) over aluminum-neodymium (Al-Nd) alloy is widely used for gate-metal lines in thin-film transistor liquid crystal displays (TFT-LCD). The electrochemical characteristics of the two-layer films/electrolyte interface in alkaline TMAH solution have been investigated using electrochemical measurement and surface analytical techniques. From the experimental results, it can be deduced that the surface topography of the Al-Nd layer is sensitive to deposition temperature. The Al-Nd layer that deposited at higher temperature was difficult to be covered completely by the Mo-capped layer. Some Al active regions are exposed to alkaline TMAH solutions, and more galvanic local corrosion is induced. Lowering film-deposition temperature and covering Mo layer sufficiently have been considered to be quite effective for avoiding blemishes, as found in this study. It will be helpful to understand the corrosion behavior of double thin-film and improve the quality of metal line deposition.
Subjects
根管治療
根尖指標
電化學阻抗頻譜
endodontic treatment
apex indication
electrochemical impedance spectroscopy
Type
thesis
File(s)![Thumbnail Image]()
Loading...
Name
ntu-96-F89524072-1.pdf
Size
23.53 KB
Format
Adobe PDF
Checksum
(MD5):0c712adf1936fe2f5fb11ab8568ccb8a