ABSTRACT
BACKGROUND: Currently, acid etching and bonding technology have been widely used in clinical stomatology. Data have indicated that the main content of inorganic elements (calcium and phosphorus) has a certain difference between the dental enamel and dentin of the young and adult permanent teeth. OBJECTIVE:To measure the content of main inorganic elements, calcium and phosphorus, in the dental enamel and dentin from young and adult permanent teeth with spectrophotometry and ethylene diamine tetraacetie acid titration method. METHODS:Each 20 adult and young permanent teethin vitrowere selected. Plaster stone and water was mixed; when it was nearly dried, the teeth were verticaly cast in the mixture and the tooth surface was exposed. The models were cut into the slices using syj-200 precision cutting machine, and then the slices were put into nitric acid and dissolved through heater to prepare standard solution. At last, the concentrations of calcium and phosphorus in the hard tissue of both young and adult permanent teeth were measured with spectrophotometric method and titration method. RESULTS AND CONCLUSION:The content of calcium and phosphorus and calcium/phosphorus ratio in the hard tissue of young permanent teeth were less than those of adult permanent teeth (P < 0.05), reflecting that the organic matter content was more than that in adult permanent teeth, but their mineralized degree was inferior to that of adult permanent teeth (P < 0.05). These findings indicate that the young permanent teeth are more acid proof than the adult permanent teeth; therefore, the acid etching time can be properly prolonged for young permanent teeth in clinical treatment, in order to achieve better effects.