Dental caries is the most common disease of childhood, and is especially a problem for low-income and minority populations. It is a complex, polymicrobial disease and we do not currently have a complete understanding of its etiology. Culture-based studies have identified Streptococcus mutans and Lactobacillus species as important to the caries process. These species are known to ferment dietary carbohydrates, generating the lactic acid that demineralizes tooth structure. More recent studies using molecular methods have made it possible to identify oral microbiome inhabits without the use of selective culture techniques.
The goals of these studies were to use open-ended molecular techniques to identify bacteria that are associated with dental caries and health in three populations: incipient early childhood caries of infants and toddlers, severe caries in the primary dentition, and severe caries in the permanent dentition. Plaque samples were collected from the surface of intact enamel for the healthy control groups and from four types of sites in caries subjects (when present): intact enamel, white spot lesions, cavitated lesions, and dentin. 16S cloning and sequencing using universal PCR primers were used to identify the bacteria present in plaque samples. Maximum likelihood phylogenetic trees with bootstrap cutoffs were used to define taxa. Data were analyzed using PROC MIXED.
In incipient early childhood caries, S. mutans, S. vestibularis salivarius, S. sobrinus, S. parasanguinis~oralis and Veillonella atypica dispar parvula were associated with caries. In severe early childhood caries, S. mutans, S. vestibularis salivarius , and S. parasanguinis~oralis were again associated with caries. Additionally, Lactobacillus, Propionibacterium, Mitsuokella , and Parascardovia species that were rarely seen in incipient lesions were associated with caries. In severe lesions of the permanent teeth, Lactobacillus species became very important. Only Lactobacillus and Propionibacterium FMA5 were significantly associated with caries in the permanent dentition. In all three studies, many health-associated species were identified, some whose role in the oral microbiome is well-established in the literature, and many others that have not been previously associated with health. In general the data supported an ecological plaque hypothesis, which states that caries is the result of an ecological shift, with caries pathogens eliminating acid-sensitive species from a healthy biofilm.
Having a complete understanding of the microbes associated with caries and health during childhood is imperative to developing interventions and treatments. Based on the typical microbial profiles seen in children, screening strategies may be developed to identify children who may be susceptible to dental caries. This screening tool could identify over-represented potential pathogens or the loss of important health-associated species.