The histology and microbiology of acute occlusal dentine lesions in human permanent molar teeth.

Acute occlusal caries of molar teeth was investigated and on microscopic examination a pattern was seen in the bacterial invasion of the tissue. A primary wave of bacterial attack, found by bacteriological isolation techniques to consist of homofermentative lactobacilli, was demonstrated at the advancing periphery of the lesion. A secondary wave of mixed superinfection followed the primary invasion. The two zones of infection could be clearly identified because there was a bacteria-free interval between them and because there were histological characteristics exclusive to each.