Deep bacterial penetration of early proximal caries lesions in young human premolars.

The aim of the study was to assess the frequency and extent of bacterial invasion in proximal small caries lesions of young human premolars. The teeth were fractured longitudinally through the lesion and examined under a scanning electron microscope. In two out of twelve teeth with incipient caries and without any cavitation, bacteria could be seen in both enamel and dentin; in one, penetrating the dentin to a depth of 1.5 mm from the dentinoenamel junction. In both lesions the chaulkiness extended to about half of the enamel thickness.