In this paper the relation between the average lesion depth (1) of artificial carious lesions and the length of microhardness indentations (D) on the surface (the load perpendicular to the surface) is investigated. The results show that an empirical linear relationship does exist between 1 and D for both human and bovine enamel. Linearity has been found for decalcification periods 2–8 days and pH values 4.5 and 4.0. The slope of the curves as well as the load dependency is discussed. The error in the lesion depth determinations is 10–15%. The study also gives a numerical comparison between the average lesion depth in human and in bovine enamel decalcified under the same conditions. After 4 days at pH 4.5 or 4.0, the relations are 1 (bovine) ≈ 1.4 # 1(human) and 1 (bovine) ≈ 1 (human), respectively. The advantage of the technique presented here is that is does not destroy the specimen and is suitable for experiments in in vivo situations.

Shallow initial enamel lesions approximately 50 μm in depth were experimentally induced by plaque in sound intact human enamel. The lesions were subsequently remineralized in vivo without any fluoride treatment for periods of 1.5 and 3 months, respectively. 11 participants carried enamel blocks in a dental appliance. To induce demineralization the enamel was placed in a well about 1.5 mm under the polymer surface to facilitate the accumulation of cariogenic plaque. In the remineralizing stages each participant remineralized the lesions previously induced in his own oral cavity as well as specimens demineralized by other participants. For remineralization the enamel was placed flush with the polymer surface of the appliance. The results were evaluated by means of microradiography and showed that after 6 weeks the mean lesion depth was 47 ± 2 μm while the mineral loss ΔZ was 1,284 ± 513 vol% × μm. After 6 weeks of remineralization about 80% of the specimens remineralized significantly; however, 20% continued to demineralize. The results suggest that natural remineralization is more dependent on a subject’s individual oral environment than by the properties of the enamel.

The purpose of this study was to compare the F^–– acquisition of enamel of APF solutions, NH₄F containing solutions, organic fluoride solutions and a urethane lacquer-containing silane fluoride. The F^–– content as a function of the distance from the anatomical surface was studied after one application, after 24 h of washing in tap water and after 1 week of washing. The results indicate that one treatment with the F^–– containing lacquer introduces an amount of permanently deposited fluoride comparable to that of a great number of applications by the other solutions mentioned. The silane fluoride-containing lacquer introduces about 2,000 ppm of permanently bonded F^–– in an average surface of 8 μm thickness.

In this study, Knoop hardness experiments on artificial carious enamel (pH 5.0, 4.5 and 4.0) are presented with the load perpendicular to the subsurface lesion. The results show that for human and bovine enamel the indentation length is proportional to the square root of the load. The proportionality constant is numerically estimated for all pH values for human and bovine enamel. The indentation measurements reflect the decalcification despite the presence of surface layer covering the lesion.

In this paper the interaction of urea on plaque-free sound human enamel is described. In 1 week urea penetrates in the enamel several hundred micrometers. It weakens or destroys part of the peptide structure, especially interprismatically. Urea does not or not measurably attack the organic matrix between the crystallites. Due to the urea interaction organic material normally plugging natural defects in the enamel surface, especially in the perikymata, is removed.