**1. Introduction**

Microbiological analysis of oral microbiota is still a challenge the science has to face. Up to this day, we have knowledge of only a portion of microorganisms living in the oral cavity. Their research is very important from the point of view of prevention, diagnostic and treatment of oral and general diseases [1]. Dental caries is the most common chronic disease in the world affecting people regardless of sex, age and ethnic origin, although it affects more the individuals with low social-economic status. *Streptococcus mutans* was identified as the causative agent of this disease. Presented were also results indicating participation of acidogenic bacteria in the process of its development [1]. These bacteria are generally called cariogenic bacteria. However, no pathogen is the direct and only cause of the development of dental caries or periodontitis. More profound knowledge of microbial composition of the oral biofilm of humans on the surface of teeth or in the subgingival space can help to understand better the complexity of pathogenesis of the development of dental diseases, and find new ways how to affect positively the oral health through balanced, physiologically beneficial microbiota [2]. The oral cavity is a constantly changing habitat. Traditional methods intended for the studies of diversity of mirobiocenoses are based on conventional isolation of bacteria by cultivation, their morphology and identification by means of their biochemical properties. These methods do not suffice to ensure concise characterisation and quantification of microbiota, are time demanding, provide results not earlier than after 48 hours and involve only cultivable bacteria. High percentage of bacteria is cultivated only with difficulties due to unknown requirements on their growth [2]. Currently, a number of genetic techniques intended for quantification, identification and characterisation of bacterial communities are available. The study of the external influence on oral cavity microbiocenosis is inevitable due to high incidence and prevalence of dental caries or periodontopathies, despite the current widespread use of oral hygiene preparations [3]. Today's market offers a multitude of such preparations, and also, alternative approaches for the improvement of oral health are available. Scientific studies presented interesting knowledge about beneficial bacteria capable of inhibiting the growth of pathogenic bacteria by their bioactive products. This concerns, for example, the proof of the suppression of oral pathogens by *Streptococcus salivarius* K12 probiotic bacteria, or their bioactive compounds can serve as a basis for the development of new strategies contributing to prevention and treatment of oral diseases [4].
