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Quantitative TLC Analysis of Dental Alloys Based on Micro-Anodic Sampling and Video Densitometry

In the corrosively aggressive medium of the oral cavity, it is recommended to use dental alloys identical to the existing permanent denture (if there is any), because the use of alloys of different composition may cause oral galvanism. Therefore, it is important to identify the composition of existing metal construction directly in patient's mouth. A simple method based on micro-anodic sampling and thin-layer chromatography was proposed for the identification of nickel-chromium and cobalt-chromium dental alloys. In situ anodic dissolution of dental alloy, induced by a direct current in an appropriate electrolyte, allows intra-oral analysis of permanent dental prostheses without destruction. Several electrolytes were tested, such as aqueous solution of HCl, HNO3, NaCl and NH4Cl. Subsequent separation and identification of dissolved metals were performed on cellulose precoated layers using different mobile phases depending on alloy composition. Quantification of separated zones was performed with CAMAG video-imaging system. Its performance were tested in both, reflectance and transmission mode. The objectives of this work were: (i) to optimize the composition and concentration of electrolyte solution, as well as the duration of sampling in order to achieve the maximum dissolution of alloy constituents, (ii) to determine the conditions for chromatographic separation of main alloy constituents, (iii) to determine the optimal instruments settings in video densitometric quantification, and (iv) to test the precision and accuracy of the proposed method on several commercially available dental alloys.

dental alloys; anodic sampling; TLC; video densitometry

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