Microbial invasion and subsurface colonization of rat enamel in early fissure caries observed by scanning electron microscopy.

In order to find out whether microbes can be detected in the incipient rat caries lesions underneath the visibly intact enamel surface, the maxilla of OM-rats, fed a cariogenic diet, were fixed and partially bisected sagittally with a thin saw. The individual teeth were finally split with a knife to get a crack surface from the fissure region. Selected tooth halves showing slight carious changes at the dentin-enamel junction were prepared for SEM and examined. In many preparations, colonies of organisms were found firmly attached to the crack surface. Single, predominantly coccus-like organisms and a few rods could be seen mostly located in the interprismatic furrows at varying depth throughout the enamel. Some lacuna-like hollows, with or without the occupant organisms, could be seen carved in the prism structure. The enamel side of the DEJ in the lesion area could be completely covered by the microbes. In samples representing arrested caries, amorphous precipitates were found at the interprismatic substance of the DEJ region.