What is ‘Selection Pressure’? (And what does it have to do with me!?)

by Dr. V Kim Kutsch

One of the primary misconceptions about the decay process is that folks seem to confuse what is actually causing, or selecting for demineralization. The term is selection pressure:

Selection pressure can be regarded as a force that causes a particular organism to evolve in a certain direction. It is not a physical force, but an interaction between natural variation in a species and factors in its environment that cause a certain form to have an advantage over the others. This can be thought of as a “pressure” that pushes the evolution of that organism toward a greater prevalence of this variation.  

While most people consider sugar to be the main culprit responsible for tooth decay, it is actually the acids produced when the biofilm bacteria metabolize the sugar which becomes the basis for the disease. Cariogenic bacteria are both acidogenic and aciduric by nature. They all share adaptive mechanisms to that allow them to exist and thrive in low pH conditions. The low pH selects for bacteria that are acidogenic/aciduric and at the same time dissolves the calcium and phosphate from the teeth. The pH therefore is the selection pressure, not the sugar. So to reverse the process, therapeutically raising the pH of the biofilm, the selection pressure is reversed and calcium and phosphate ions re-enter the enamel. Raising the pH encourages the growth of healthy bacteria and also drives remineralization.