[Difference between dental plaque formation by Lactobacillus Sp. and Strep. mutans].

Human teeth were suspended in a basal medium with sucrose 10%; they were incudated for formation of dental plaques "in vitro". The microorganisms used were: Strep. mutans, Lactobacillus salivarius var. salivarius and a mixture of them. The following aspects were stablishad by scanning electron microscopy: 1) The teeth inoculated with Strep. mutans had coccoid forms, lying on an organic film with spheric spaces in some sectors, and irreguar forms in others (Fig. 1). 2) The teeth inoculated with Lactobacillus salivarius had rod forms attached to the adamantine surface (Fig. 2, 3). 3) Teeth incubated with the mixutre had rod forms over a granular film (Fig. 4). 4) The control teath did not have plaque (Fig. 5). This experience shows that the extracellular polisacharide, reticulated or granular (mutano) appeared only in teeth incubated with Strep. mutans alone (Fig. 1) or mixed with Lactobacillus (Fig. 4). On the other hand Lactobacillus appeared attached on the enamel surfaces, perhaps due to cohesive adhesive forces (Fig. 2). Two different interpretation or the formation of dental plaques that take place on the enamel free surfaces of teeth are presented.