[Experimental analytical electron microscopic studies on the quantitative analysis of elemental concentrations in biological thin specimens and its application to dental science].

Abstract

The aim of this study is to employ an energy dispersive X-ray spectrometer (EDS) in developing a computer software system for the quantitative analysis of elemental concentrations in biological specimens. The methods and the software were applied to the examination of the coronal dentin of human deciduous and permanent teeth. Results 1. Examination methods. Chemical compounds known for their calcium (Ca) and phosphorus (P) contents were used to determine optimum conditions for analysis. The following were the best analytical conditions: 100 kV accelerating voltage, 2 x 10(-10) A probe current, 10 ekV energy scale, 100 sec. counting time, and 100-150 nm section thickness. Under these conditions, it is possible to obtain statistically sufficient integral spectra values. By calculating with the computer software(t-factor) developed in this study, it was possible to arrive at analytical calcium and phosphorus concentration values that are very close to theoretical values. 2. Application to human dentin. Deciduous intertubular dentin contained 24.9% (w/w) Ca and 12.1% (w/w) P; peritubular dentin in the same teeth contained 30.7% (w/w) Ca and 15.3% (w/w) P. Permanent intertubular dentin contained 25.5% (w/w) Ca and 12.5% (w/w) P; peritubular dentin in the same teeth contained 34.5% (w/w) Ca and 16.9% (w/w) P. These results show that, in both permanent and deciduous teeth, concentrations of Ca and P are higher in peritubular than in intertubular dentin. Concentrations Ca and P in both peritubular and intertubular dentin are lower in deciduous than in permanent teeth. The computer software developed for this study differs from chemical analysis and may prove very useful in microanalysis of mineralized tissues on the basis of their ultrastructures.