The aim of the study was mapping of the chemical elements on the enamel surface for the identification of the distinct phases, of the uniformity and dispersion of the compounding elements, as well as qualitative and quantitative analysis of some enamel constituents, both prior to and after acid etching with orthophosphoric acid with various action times.
Materials and method: 15 molars with no carious lesions had been axially sectioned in vestibulo-oral direction, using edged active diamond disks at conventional speeds, under continuous cooling with water, two halves being thus obtained. The external surface of the enamel was covered with a varnish resistant to acid action, with the exception of some square, 3 mm-sided zones, situated in the central area of the proximal sides. The 30 sections were randomly divided into 3 groups. The reference was represented by 10 dental sections not subjected to acid etching. Each of the 2 experimental groups was formed of 10 sections etched for 15 and, respectively, 30 sec, with 37% orthophosphoric acid. The sections were analyzed on a scanning electronic microscope (VEGA II LSH, Tescan Czech Republic), coupled to a QUANTAX QX2 (Bruker/Roentec, Germany) type EDX detector.
Results. A preponderent and uniform charging with the two main elements of hydroxypathite: Ca and P, followed by Mg, Na and Cl, could be observed over the whole enamel surface. The highest decrease in the average concentration of the calcium ions was registered after enamel etching for 30 sec (namely, from 51.34% in weight, in the case of non-etched samples, to 38.71% in the etched ones). As to the concentrations of the phosphorous ions, the same decreasing tendency of the average values was noticed after acid etching (from 20.38% in non-etched samples to 17.79% in the samples subjected to acid etching for 15 sec, and to 16.82%, respectively, in the samples etched for 30 sec).
Conclusions. Elimination of the compounding elements of enamel increases with increasing the time of acid etching, while the loss of the calcium and phosphorous ions was not significant after etching for 15 and 30 sec.
- acid etching
- calcium
- enamel
- phosphate