Learning more about the causes of tooth decay

Learning more about the causes of tooth decay

What leads to this all-too-common condition

Dental caries, or tooth decay, is the result of chronic solubilization of tooth minerals from acid produced by bacteria adhering to the tooth surface. The etiology of caries is based on a four-factor theory that includes oral microorganisms, oral environment, host, and time. There are over 700 microbial species colonizing the human mouth. Streptococcus mutans, a bacteria known for producing acid from fermentable carbohydrates (sugar), has traditionally been identified as the putative pathogenic organism in dental caries. However, the notion of dental caries being the result of multiple organisms was postulated by W.D. Miller as far back as 1890. Lactobacillus acidophilus was implicated by Jay in 1937. Evidence shows that bacterial species of the genera Veillonella, Scardovia, Lactobacillus, and Propionibacterium may contribute to cariogenic conditions in the oral cavity. A recently published study suggests that S. sputigena can significantly boost the cariogenicity of S. mutans.

Selenomonas genus has previously been identified in dental caries. The latest study is the first to identify a cavity-causing role for a specific Selenomonas species. S. sputigena is only one of several caries-linked bacterial species in plaque besides S. mutans but does not cause caries alone.  S. sputigena is a flagellated gram-negative anaerobic bacterium with small appendages that become trapped by glucans, making honeycomb-shaped “superstructures” that encapsulate and protect S. mutans. This results in increased acid production and thus worsens caries severity. S. sputigena has previously been identified as a pathogen in chronic and aggressive periodontitis.

This study is significant since it illustrates the complexity of the caries process and helps to understand why some patients with a high caries rate exhibit low levels of S. mutans. It also highlights the complex biodiversity of the caries process, lending support to the notion that caries is more complicated than just a single bacterial infection.  More comprehensive understanding of the etiology and pathogenesis of dental caries will lead to better preventative measures. The identification of this new co-pathogen is a step towards that end.


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