Microbiology of Dental Caries: A Literature Review

Aim: to review the current knowledge on dental caries microbiology and critically appraise the literature. Methodology: An electronic search of the available dental literature was done using different databases (PubMed, Google Scholar, Scopus). The following keywords were used: dental caries, carcinogenic bacteria and oral biofilm. In addition, classic textbooks that related to dental caries and oral microbiology were searched. Findings: Oral bacteria can grow in two ways: in planktonic or biofilm forms. In the past, most microbial studies were studies of the planktonic form. Only around 0.1% of oral bacteria grow in the planktonic state. Bacterial cells usually aggregate and attach to the tooth surface to form an oral biofilm. The polysaccharides in the biofilm matrix are a resource that acidogenic bacteria metabolise and produce acids to initiate or progress the dental caries lesion. Different types of acids are created as a result of biofilm metabolism, which cause a shift in oral pH under the critical level. This reduction in the pH level will influence the chemical composition of the tooth surface. The bacterial cells start to multiply to form a microcolony within 24 hours. If left undisturbed the growth is continued, resulting in a mature type of biofilm within a week. Summary of findings: The most frequent species found associated with dental caries were mutans streptococci and lactobacilli, which shift the balance towards tooth tissue demineralisation.