Colonization of microenvironments
The oral cavity consists of several major and minor compartments, each constituting a separate microenvironment not easily affected by major events in the oral cavity.
Examples of major compartments are the tongue, the oral mucosa, and the tonsils. The different approximal tooth surfaces, occlusal fissures, and gingival sulci are regarded as minor compartments.
A specific area that supports a bacterial flora is termed a habitat. The flora of a habitat develops through a series of stages, collectively called colonization. Colonization is a complex process, because it involves not only interaction between bacteria and their environment but also interactions among different bacteria. The first important prerequisite for colonization is access. The organisms must be able to enter the habitat and consequently they must be able to be transmitted from one habitat to another. For example, mothers can serve as reservoirs for oral bacteria, which they transmit to their children. Within a single host, bacterial reservoirs can aid survival of the organism.
In the human mouth, not only the oral mucosa but also the tongue and tonsils may serve as as reservoirs for bacteria, which, under favorable conditions, may colonize the teeth as well as the periodontal pockets. It is well known that the dorsum of the tongue is the main reservoir for Streptococcus salivarius, which is a very potent, cariogenic (acidogenic) bacteria. In one study, however, higher numbers of S mutans were repeatedly found on the dorsum of the tongue after five thorough scrapings with a tongue scraper than prior to scraping, indicating this to be an important reservoir (Axelsson et al, 1987). Lindquist et al (1989) found a significant correlation between the prevalence of S mutans in saliva and its prevalence on the dorsum of the tongue.
These data support the inclusion of the dorsum of the tongue in oral hygiene procedures, at least in patients highly infected by periopathogens and/or cariogenic bacteria, such as S mutans.
Although there are general definitions of habitats, studies of the oral microflora should always include careful definition of the habitats being examined. It is important to recognize that the physical dimensions of a habitat do not fall within specific limits: The whole oral cavity, an occlusal tooth surface, or even a defined area on the occlusal surface may be considered a habitat. In oral microbiology, changes in the flora of a habitat such as the saliva may indicate, for example, patients at risk of developing caries, while changes in tooth surface microenvironments can
identify a surface at risk of disease.
