Frequency of dental exposure to carcinogenic (acidic) environments affects the likelihood of developing dental caries.[32] After meals or snacks, the bacteria in the mouth metabolize the sugar, creating an acidic by-product that lowers the pH. As time progresses, the pH returns to normal due to the buffering ability of saliva and the dissolved mineral content of the tooth surfaces. During each exposure to an acidic environment, portions of the inorganic mineral content on the surface of the teeth dissolve and can remain dissolved for up to two hours.[33] Since the teeth are vulnerable during these acidic periods, the development of tooth decay is highly dependent on the frequency of exposure to the acid.
This critical process can begin within days of the eruption of teeth in the mouth if the diet is sufficiently rich in suitable carbohydrates. Evidence suggests that the introduction of fluoride treatments has slowed the process.[34] Proximal caries takes an average of four years to pass through the enamel of permanent teeth. Because the cement that coats the root surface is not nearly as durable as the enamel that coats the crown, root caries tends to progress much more rapidly than decay on other surfaces. Progression and loss of mineralization at the root surface is two and a half times faster than enamel caries. In severe cases where oral hygiene is very poor and where the diet is rich in fermentable carbohydrates, caries may cause tooth decay within months of tooth eruption. This can happen, for example, when children constantly drink sugary drinks from baby bottles (see later discussion).
