Dental caries is one of the most common chronic and multifactorial diseases affecting the human population. The appearance of a caries lesion is determined by the coexistence of three main factors: (i) acidogenic and acidophilic microorganisms, (ii) carbohydrates derived from the diet, and (iii) host factors, in particular the nature and composition of saliva, tooth sensitivity, and age. Socio-economic and behavioral factors also play an important role in the etiology of the disease.
Caries develops as a result of an ecological imbalance in the stable oral microflora. Cariogenic microorganisms produce lactic, formic, acetic and propionic acids, which are a product of carbohydrate metabolism. Their presence causes a decrease in pH level below 5.5, i.e. below the critical pH, resulting in demineralization of enamel hydroxyapatite crystals and proteolytic breakdown of the structure of tooth hard tissues. Streptococcus mutans, other streptococci of the so-called non-mutans streptococci group, Actinomyces and Lactobacillus play a key role in this process.
Oral microorganisms form dental plaque on the surface of teeth, which is the cause of the caries process, and shows features of the classic biofilm. Biofilm is a dynamic structure that is constantly active metabolically. In healthy conditions, the alternating processes of decrease and increase of biofilm pH occur, which are followed by the respective processes of de- and remineralisation of the tooth surface. In healthy conditions, these processes are in balance and no permanent damage to the tooth enamel surface occurs.