A quantitative chemical distribution of five elements in several undecalcified sections of teeth was determined by the electron microprobe method. The calcium (Ca)! phosphorus (P) weight percent ratios were determined in scans through the enamel and dentin, and characteristic curves for the concentration of the trace elements magnesium (Mg), sodium (Na), and chlorine (Cl) were obtained.The electron microprobe permits the qualitative and quantitative analysis of elements in a continuing or spot scan of an extremely smooth dental or other mineralized surface. This instrument has been widely and successfully used in the fields of metallurgy and geology and in the study of semiconductors. Smith and co-workers'-5 have developed correction formulae for quantitative analyses of chemically complex systems and have shown that values obtained are accurate within 1-5%.Several laboratories have been doing biological analyses using the microprobe from the time it was first marketed in this country. The earlier work was primarily on samples that could be analyzed for elements heavier than sodium and was generally limited to biologically hard parts such as bone.6 Hoerman et a17 have reported the uptake of tin and fluorine in human enamel in situ by the topical applications of stannous fluoride. Tin concentrations were determined by the electron microprobe, and fluorine (F) determinations were made chemically. Their report demonstrates the use of the electron probe for the analysis of certain elements in calcified tooth sections.Frank, Capitant and Gonis reported electron microprobe analyses of Ca, P, and Cl in anorganic tooth tissues impregnated with KI to establish uniformity in density, espe-
1. Hazards of the indirect impression techniques for crown fabrication are discussed. 2. A foreign body reaction caused by retained cotton fibers is substantiated. 3. Since the gingival retraction cord is a possible and likely source, placing the cord and choice of instruments is important.
A detailed electron microprobe analysis of Ca, P, Na, Cl, and Mg in three early carious lesions is compared with data of these elements found in noncarious enamel of the same three specimens.
Dispersion staining and the Becke Line Method were used to obtain refractive index values from undecalcified sections of 20 human tooth specimens that exhibited early carious lesions. Characteristic dispersion staining curves and dispersion curves for noncarious enamel, the zone of deepest penetration in carious enamel, and carious enamel external to the deepest zone, are presented.
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