Column-like structures of human dentin in carious and artificial lesions.

Serial sections of 36 human teeth with minor to medium-sized carious lesions, adequate sections from previous studies of artificial lesions adjacent to fillings of amalgam (AM), silicate cement (SI) and glass ionomer cement (GI) were studied by ordinary light microscopy and microradiography. Six artificial primary root lesions were included. In carious lesions, dentin columns were visible in the demineralization zone and partly also in the translucent/radiopaque zone. A typical feature of the artificial lesions adjacent to SI fillings was highly radiopaque columns alternating with radiolucent ones. In the GI group such columns were seen at the cavity wall and the advancing front of the outer lesion. In the AM group dark columns were unveiled as pegs in the latter localization. The findings led to the assumption that the dark columns of intact dentin are preferred pathways of acid diffusion in artificial and, possibly, carious lesions. Increased radiopacity of columns in the SI and GI groups is explained by continued exposure of the tooth surface to fluoride dissolved from these fluoride-rich filling materials.