Demineralization and Remineralization Phenomena of Human Enamel in Acid Erosion Model

Abstract

In this study, in vitro experiments were conducted using an acid erosion model to investigate and compare changes in enamel demineralization over time in different age groups. A total of 34 human extracted teeth with no caries were used, 17 of which came from subjects in their 20s at the time of extraction and 17 from subjects in their 60s. To measure the depth and the volume of enamel demineralization, the teeth were immersed in demineralization solution (0.1 N HCl) for durations of 30 seconds, two minutes, one hour and five hours. In terms of the results, one important finding was that on the outermost layer of the enamel exposed to the acidic solution, an acid resistance layer was observed after only 30 seconds of exposure and after up to five hours of exposure. Detailed investigation of this hypermineralized layer revealed that the molar ratio for Ca/P was 1.16 ± 0.02, the width of the layer was 0.9 ± 0.2 m, and dense depositions of large and small quadrilateral crystals were observed. Another important result is that the volume of enamel lost per second of exposure to the demineralization solution initially declined exponentially over time, with the largest rate of loss observed at 30 seconds of demineralization, after which the demineralization time increased and a tendency was seen for a state of equilibrium to be reached. Based on the results of this study using an acid erosion model, we conclude that while the demineralization solution penetrated into the interior of the enamel even after only a few seconds of exposure, minerals eluted from the crystals were confirmed to have been remineralized. In terms of age, enamel demineralization was not considerably influenced by age since no statistically significant differences in demineralization depth or volume were observed between the 20s and 60s age groups.

Evaluation of Enamel Surface Morphology and Microhardness after the Application of Different Protective Agents

“…It is reported that time and frequent exposure to a solution below the critical pH of 5.5 causes erosion in dental enamel 7,8) . Tooth erosion may be due to internal and external factors 9) .…”

The Micrograph Image of Early Experimental Dental Caries in Permanent Teeth in Hanoi Medical University

“…Some authors only used acidic solution to damage the early stages of tooth decay, but without the protective factors, the lesions created were similar to erosion lesions than caries. 3,6 There are many ways to evaluate the loss of enamel minerals such as visual examination, X-ray, hardness measurement of enamel surface, using polarized light, using fluorescent light of DIAGNOdent laser, observations under SEM. 7 This study used the ICDAS visual criteria for detecting caries lesions and observed under a scanning electronic microscope SEM.…”

“…The enlargement of enamel sheath results in a way surface to subsurface layer of the carious lesion. 1,3 Dental caries that is diagnosed and treated early will decrease the cost of treatment and the effectiveness will be higher. 2 Study on the structure and the mechanism of the formation of early caries is an important subject for evaluating the caries-preventive methods.…”

Acidic Calcium Phosphate Crystals Observed on the Outermost Layer of Human Enamel

“…In demineralized layers containing H + ions, circulation occurs due to the concentration gradient of anions and cations in a closed system; thus, when a decline in H + concentration does not occur, demineralization progresses 13,14) . In Hayashi's 15) in-vitro acid-erosion model experiment on human enamel, most of the minerals were eluted from the crystal due to the demineralization of enamel. At the same time, the study confirmed that a portion of the minerals was re-deposited as a thin layer on the outermost surface of the tooth.…”