New qualitative methods of diagnosis are used now in dental practice. Very popular are saliva diagnostic tests. They are fast and convenient for use. By the saliva one can make diagnosis on the caries activity because of wrong diet (Lactobacillus bacteria in saliva), elevated level of cariogenic microorganisms in saliva (Streptococcus mutans level in saliva) and saliva pH. It is possible to detect the level of Streptococcus mutans and Lactobacillus in saliva using selective diagnostic medium for the bacterial culture.