ABSTRACT
<p><b>OBJECTIVE</b>To analyze the count of Streptococcus mutans (S. mutans) and Lactobacilli (LB) in different groups and the cases in dental caries. To research the synergistic effect of S. mutans and LB in the process of dental caries.</p><p><b>METHODS</b>110 cases with dental caries were selected and divided according to the different degree of caries, nature and ages. To culture bacteria in the selective culture medium, then count the number of colonies. The detection rate of two kinds of bacteria in different groups, means of the bacteria count and the cariogenic cases were analyzed.</p><p><b>RESULTS</b>The means of the two bacteria count increased along with the degree of caries increased (P < 0.05), and increased in the older group (P < 0.05) and the active stage (P < 0.05). The cases of two bacteria increased with the degree of caries increased (P < 0.05), and increased in the older group (P < 0.05). But there were no significant differences in evolution period and arrested caries.</p><p><b>CONCLUSION</b>The pathopoiesis capability of S. mutans and LB enhanced with the extent of caries increased. In the older group, their synergism role play a lead position. In evolution period and arrested caries, S. mutans and LB were difference only in quantity and their solo cariogenic potential all enhanced in active stage, but there were not correlation on pathopoiesis capability and active or stationary phase.</p>