The Rise and Impending Fall of the Dental Cavity

Summary

Cavities are a communicable disease, and if you’re among the 90% of Americans who’s ever had one, you probably got them from your mother.This isn’t to say that you were directly infected with cavities by your mother, but that due to the everyday interactions where parents end up exchanging spit with their children, at some point, your oral microbiome probably came to resemble hers. You share food, you share drinks, you share utensils and silverware, and as a result, your clean infant mouth was eventually colonized by your mother’s strain of the main cavity-causing bacteria Streptococcus mutans.After S. mutans has taken up residence in your gluttonous abode, that’s when the magic happens.S. mutans is a carbaholic—it absolutely loves carbs. The primary way it gets its energy is through using the magic of glycolysis to break down sugar, bread, and everything else it can touch, producing several acidic byproducts in the process. The main organic acid produced as a result of S. mutans’ feeding is lactic acid.With lactic acid in your mouth, the pH falls, leaving your mouth more acidic and hostile to its mineral inhabits—your teeth. The acidified environment begins to demineralize tooth enamel, making it rough, causing pits to form and widen. When those pits are large enough, that’s a cavity.This process has been shown experimentally in vivid detail. In the journal Dental Materials, Cross et al. presented profilometry images of what happens to teeth after exposure to a 30% lactic acid solution. The result of doing this is shown in images a, b, c, and d, below, which are, respectively, polished enamel and the same enamel after 45, 90, and 225 minutes. It clearly becomes much less smooth and vastly more rough as time in the acid continues. You’ll also notice images e and f, which are, respectively, another clean enamel surface and the same surface after 72 hours of colonization by S. mutans.Cross et al. (2009), Figure 3Acidic environments rip through teeth, and the other bac...