Abstract
White lesions represent an early phase of caries formation. 20 human sound premolars were subjected to pH cycling procedure to induce subsurface lesions (SLs) in vitro. In addition, 2 teeth with naturally developed white spot lesions (WSLs) were used as references. All specimens characterized by confocal Raman microscopy being used for the first time in examining white & subsurface lesions and providing a high resolution chemical and morphological map based on phosphate peak intensity alterations at 960 cm−1. Nanoindentation technique was used to measure Hardness (H) and Young’s modulus (E) of enamel. Phosphate map of examined samples exhibited presence of intact surface layer (ISL) followed by severe depletion in (PO43−) peak in the area corresponding to the body of the lesion. In all examined groups, the mechanical properties of enamel were decreased in lesion area and found to be inversely related to penetration depth of indenter owing to enamel hierarchical structure. By combining the above two techniques, we linked mechanical properties of enamel to its chemical composition and ensured that the two methods are highly sensitive to detect small changes in enamel composition. Further work is required to bring these two excellent tools to clinical application to perceive carious lesions at an early stage of development.
Highlights
White lesions represent an early phase of caries formation. 20 human sound premolars were subjected to pH cycling procedure to induce subsurface lesions (SLs) in vitro
Images constructed via K-mean cluster analysis (KMCA) demonstrating clusters with four distinguished colors: acrylic resin, sound enamel with two different intensities of phosphate and demineralized lesion body
Curves were derived from different indentations made in three zones of enamel: unaffected enamel close to dentin, lesion area which is confined to enamel surface and intermediate zone which lies between the two areas to show differences in penetration depth of indenter tip
Summary
White lesions represent an early phase of caries formation. 20 human sound premolars were subjected to pH cycling procedure to induce subsurface lesions (SLs) in vitro. Subsurface enamel demineralization is known as white spot lesions (WSLs); they represent the early stage of caries formation where affected surfaces seem to be intact upon gentle probing. The dynamic nature of the process has been modeled in numerous laboratories by various pH cycling models[6,7] in an attempt to simulate intraoral conditions in which enamel is subjected to repeated sequences of de/remineralization periods. The advantage of those models is that much can be learned about the processes involved, in a shorter period of time
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