Microflora of Oral Cavity
In the oral cavity more than 1000 species of microbes are present. Less than half of them are only cultivable. Total quantity of microbes exceeds 1 billion per 1 ml of saliva. The detailed characteristics of oral microbiota are presented in the section “Microflora of oral cavity”.
A tremendous variety of saprophytic and facultatively pathogenic microorganisms (streptococci, staphylococci, diphtheroids, treponemas, fungi, protozoa and many others) is found upon oral mucosa.
The oral cavity is a favorable medium for most of the microbes; it has an optimal temperature, a sufficient amount of nutrients, and a weakly alkaline reaction.
The groups of bacteria, associated with the healthy state of dental tissues, include a vast number of streptococci (e.g., S. sanguis, S. mitis, S. gordonii, or S. intermedius) and some other bacterial species (e.g., Veillonella parvula and Actinomyces odontolyticus).
The majority of bacteria can readily attach to dental tissue forming dental plaque – a special kind of microbial biofilm. The role of oral streptococci should be emphasized here, as they produce large amounts of long-chain polysaccharides from food sugars, thereby promoting microbial adhesion.
When oral hygiene is inadequate, the deep teeth lesion, or caries develops. In conditions of food carbohydrate excess (so-called “table sugars”) cariogenic oral streptococci S. mutans and S. sobrinus metabolize sucrose and other carbohydrates with lactic acid production. Decrease of pH leads to teeth enamel decay. Various lactobacilli species promote further caries progression.
The presence of carious teeth is the condition for deep change of normal oral microbiota. It is characterized by gradual expansion of anaerobic bacteria that accelerate decaying processes. Finally, this may lead to various kinds of periodontal pathology (e.g., ginigivitis and acute or chronic periodontitis).
Among the most common pathogens, causing gingival pathology, are Prevotella intermedia, Peptostreptococcus micros, and several species from Fusobacterium genus (F. nucleatum, F. periodonticum).
The causative agents of periodontites comprise pathogenic microbial species Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola, as well as Eikenella corrodens, Aggregatibacter actinomycetemcomitans, Capnocytophaga spp., Actinomyces naeslundii and many others. They actively stimulate the progression of periodontitis resulting in tissue destruction