Pathological findings on the progression of carious lesions

Abstract

Dental caries are classified histopathologically into enamel caries, dentin caries and cementum caries. We observed these caries using established methods and confocal laser scanning microscopy (CLSM). In early enamel caries, subsurface decalcification was observed, demineralization and remineralization occurred, and several zones could be distinguished. Using CLSM, the remaining enamel rod structures were observed in the surface zone. Destruction of enamel rods was seen in the body of the lesion. Enamel rods and cross striations were observed clearly in the dark and translucent zones. The lesion progressed along the enamel rods in two patterns : one along the heads of enamel rods, and the other along the tails. Another mode of progression in enamel caries was along the incremental Retzius lines and enamel lamellae. However, on the basis of radiographic studies there was no direct correlation between the occurrence of enamel lamellae and caries. Once dental caries reached the dentino-enamel junction, they quickly undermined sound enamel. In dentin caries, the lesion progressed along the dentinal tubules and lateral branches, and softened dentin was observed. Cuboidal or rhomboid-shaped mineral crystallites were observed by SEM in the dentinal tubules beneath the carious lesion. Therefore, the dentinal tubules seemed to be related both to demineralization and remineralization. Cementum caries progressed along Sharpey's fibers, the lamellated appearance began to disappear, and the surface of the cementum was destroyed.