I'm cavity-prone. It doesn't seem to matter how often I brush (twice a day) or floss (once) or visit the dentist for cleanings (every 4-6 months), I still end up with cavities. It's my genes, I'm told. There's not much I can do but follow my dentist's advice and cross my fingers. Now that may all be changing. New research has identified an enzyme, present in the human mouth and intestinal tract, which adheres to teeth and breaks down sugars -- and in the process, secretes a by-product acid that decays teeth. Well, something like that. From an article about the research:

The University of Groningen researchers analysed the lactic acid bacterium Lactobacillus reuteri, which is present in the human mouth and digestive tract. The bacteria use the glucansucrase enzyme to convert sugar from food into long, sticky sugar chains. They use this glue to attach themselves to tooth enamel. The main cause of tooth decay, the bacterium Streptococcus mutans, also uses this enzyme. Once attached to tooth enamel, these bacteria ferment sugars, releasing acids that dissolve the calcium in teeth. This is how cavities develop.

The important thing is that now that we know this, it's only a matter of time, scientists speculate, before we find a substance which inhibits the enzyme. All we have to do is put this substance in toothpaste and hope it doesn't have horrible side-effects! You could even put it in candy -- and tooth decay would be a thing of the past.