A structural analysis of approximal enamel caries lesions and subjacent dentin reactions.

The present study examines the correlation between caries lesions in enamel and the corresponding dentin reactions in proximal tooth surfaces with lesions ranging from enamel lesions to cavitations without dentin exposure. Using quantitative inhibition technique, the highest degree of tissue porosity, irrespective of lesion activity, was always noted along a Central-Traverse (CT), which followed the direction of the rods from the deepest point of penetration to the surface. The conical shape of approximal enamel lesions can thus be seen as the result of systematic variations in porosity along the rods determined by the specific interproximal environment. The initial dentin reaction, related to the enamel lesion approaching the enamel-dentin junction (EDJ), was seen as a local dentin translucency where the CT crossed the EDJ. Results from histomorphometric analyses revealed that, when the enamel lesions reached the EDJ, brownish discoloration in the dentin never exceeded the histologic contact area between the enamel lesion and the EDJ. In relation to the less advanced parts of the individual enamel lesion, the dentin responded with formation of translucent dentin. These reactions did not occur beyond an area determined by lines in the direction of the rods from the peripheral part of the enamel lesion towards the EDJ. The results did not support the view that dentin caries spreads along the enamel-dentin junction. The peripheral dentin translucency is therefore generated by stimuli transmitted along the rods of the less advanced parts of the enamel lesions.